Definitive list of AHC maintenance items (2 Viewers)

[IndroCruise]

Good Afternoon Indrocruise

Back to the AHC project;

I have been going through all the suggestions and guidance as per your inputs, (sadly i am not to physically mobile) so progress is slow.

One thing i forgot to mention was that i have both inspected and tested all AHC fuses and Relays.And i have inspected the rear AHC height sensor. The rear sensor looked in almost new or perfect condition., however As yet i have not carried out the electric current test on the sensor.

I must also admit l omitted to comment clearly on the following,

Every time l insert key in ignition and go for a basic "start-up" of the vehicle, in this i mean not an "Active-Test" just a standard start up,
So Insert Key, and turn on Ignition, but do not start yet, The AHC combination indicator shows the AHC light on "LO" illuminated, there will be no "OFF" blinking, I then proceed to push the UP button and the indicator light rises up through N to Hi.

If l then stand with my hand on the AHC Motor, and ask a colleague to Start the Vehicle, the Motor give a clunk or a slight thud very soon after the vehicle is started ie within 2-4 seconds, and at the same time as the slight thud is felt, the AHC LIGHT "OFF" illuminated and the "OFF" Blinks every second.
In my opinion this feels like the AHC Motor tries to run but there is a solenoid kick in and blocks the motor from running, or causes immediate pressure build up causing the pressure sensor to kick in or close a solenoid resulting in immediate pressure build up and then the Ahc pump is instructed to close off or stop.

Sadly as yet i have not been able to get the "Active Test" to bear fruit.
I have not yet been able to get the pump to pump in "Active-Test" so therefore no oil or air comes out when i go to bleed the accumulator or any of the 4 spheres.

May i ask,
What is the precise journey of the fluid? ie, from AHC pump to "???" and from "???2" to and from "???3" to ect ect
Does the fluid from the AHC leave the AHC and go to the longish barrel shape Accumulator first, ( on my RHS chassis rail between the rear and front globes) or does it go to the Levelling Manifold before going to the main accumulator?

I ask this because i have though about ( In Active-Test Mode but very cautiously running the motor direct from a 12v supply) following the output pipe from the AHC pump to the next "Joint" and opening the pipe there to see if the AHC will pump fluid through to this point, and if it does, tighten up that pipe and go to the next point where i can open the fluid line and try follow / push the fluid through the system as far as i can.
I fully understand that normally the respective solenoids will prevent this, but is this the case while we are in "Active-Test" mode, my theory is the solenoids might not be active, or perhaps more accurately worded, they might be in an "open" state and might leave the fluid free to flow through the system.

One final question,
Is it crucial to Delete all DTC's (Diagnostic Trouble Codes) before trying any action such as "Active-Test"
Or to re-word that question, If there are still active DTC's do they or could they prevent the "Active-Test" from working.

Please bear with me, i do understand if i study the FSM i should learn these things. However i am still only finding my way through the FSM and i admit i do at times get confused.
Albeit i fully acknowledge trying to follow the FSM but operating via manual testing without a Handheld computer such as Techstream, is a serious handicap.
As yet i have not found or settled my mind on a Handheld device that will operate on my Macbook or Iphone.
i am reluctant to route out any old Mackintosh laptops, i really wish to move on with an ios compliant computer.

Thank you my dear and patient friends;

Good evening @Urtwob

You have acknowledged that

“…. operating via manual testing without a Handheld computer such as Techstream, is a serious handicap”.

This definitely is very true – and you understand that -- but it is still worthwhile to attempt some diagnosis based on the physical symptoms observed without the hints given by DTC’s observable on Techstream.

It also means the Front and Rear AHC pressures are unknown unless they have been physically measured recently with pressure gauges.

With no passengers, no load and full fuel tank(s), Front AHC pressure (by Techstream) should be in the range 6.4 Mpa to 7.4 Mpa and Rear AHC pressures (by Techstream) should be in the range 5.9 Mpa to 7.0 Mpa (assuming that you have the additional fuel sub-tank, otherwise a little lower). These numbers are approximately 1.2 Mpa higher when measured with pressure gauges as defined in the FSM in the “On-vehicle Inspection” section. See more details at:

LC100 Workshop Manual - https://lc100e.github.io/
then tabs in the left hand panel of the opening page:
Repair Manual > SUSPENSION AND AXLE > ACTIVE HEIGHT CONTROL SYSTEM > ON-VEHICLE INSPECTION

Is this a simple matter of unknown AHC pressures being excessive, causing the ECU to stop the AHC Pump??

This is possible but seems unlikely. It is clear from your description that the AHC pressures are negligible at the moment – they are nothing like the above numbers – confirmed simply by your observation that there is no flow when the bleeders are open, with or without the AHC Pump running, and with the vehicle at or near the bump-stops.

If an AHC over-pressure problem is suspected but cannot be measured, then this idea could be tested by supporting part of the weight of the vehicle on jacks, or transferring more weight to the front torsion bars (wind say five turns clockwise at the torsion bar adjusters to reduce Front AHC pressures by ~1 Mpa), then seeing whether the AHC system will operate at lesser load and pressures.

Otherwise, AHC pressures can be addressed later.

The first order of business is to discover

(1) why the AHC Pump does not run under the control of the AHC Electronic Control Unit (ECU), and also

(2) what faults are indicated by the AHC Pump not running when the ECU is by-passed using the “Active Test”.

Given all that has gone before in the previous posts, and noting that the diagnosis must proceed without Techstream or other scanner capable of reading AHC Diagnostic Trouble Codes (DTC’s) and must rely only on observed physical conditions, may I suggest the following sequence?

Some of this may already have been done – the sequence is expressed this way simply for completeness and to provide a list of items that can be ‘ticked off’ in a sequence going from ‘simple’ to ‘complicated’ in an effort to find why the AHC system is not working and to allow remediation of the problem:

1. Check that all connections at the AHC Pump and Motor are seated and tight, with connectors and harness wiring in good condition (power to Pump, connector to Pressure Sensor, connection to Temperature Sensor. The purpose is to eliminate simple problems first,

2. Test the condition of the pressure sensor next to the AHC Pump using the procedure at Page DI-219 (DTC 1718) in the FSM extract attached to Post #932 in this thread. The purpose is to be sure of the condition of the Pressure Sensor – the AHC system will not operate if it is faulty,

3. Delete all existing DTC’s and fault conditions manually using the procedure below at DLC1 in the engine bay (connect E1 and Tc) or the equivalent FSM procedure using DLC3 (Tc to CG) under the dash. Special Service Tool SST 09843-18020 and 09843-18040 are a simple wire connectors – instead suggest use an unbent paperclip or similar. The purpose is to reduce confusion by clearing DTC’s which may have arisen from previous work and which now may be irrelevant – such as when connecting and reconnecting components. The ongoing DTC’s and fault conditions will be re-established as soon as the engine is started. (Remove paperclip or other connector when finished and hold down for a few seconds the AHC “OFF” switch on centre console to re-start AHC system).

4. Perform and make written notes of ALL the “Pre-check” tests exactly as described in the attachment at Post #895 in this thread using DLC1 in the engine bay, or, the equivalent procedure using DLC3 (Tc to CG) under the dash (FSM Page DI-208), meaning ALL of

(1) DIAGNOSIS SYSTEM CHECK, and then,

(2) INPUT SIGNAL CHECK (TEST MODE CHECK), and then,

(3) DTC OF INPUT SIGNAL CHECK, and then,

(4) DAMPING FORCE CONTROLLING CONDITION CHECK, and then,

(5) HEIGHT CONTROL OPERATION CHECK (ACTIVE TEST),

and in each case being sure of the correct connections, using a simple connector such as an unbent paperclip or similar and with all doors and tailgate closed, interior lights OFF, aircon OFF, other ancilliaries OFF, steering straight ahead. The purpose is to begin the diagnosis process systematically (as a Doctor would with the human body) rather than starting with premature guesses. Then ascertain what works and what is inhibited in some way. (Again, remove paperclip or other connector when finished and hold down for a few seconds the AHC “OFF” switch on centre console to re-start AHC system).

By the way, when the instructions for the above tests in the referenced attachment or in the FSM say “Turn the ignition switch ON”, it actually means “START the engine”,

5. Given your previous observations and notes, it is possible that some, or even many, of these “Pre-check” Tests are negative (do not produce a result) and if so, that is important information to record. The purpose is to try and work out what a logical continuing process might be – a sensible process of elimination, if you like,

6. Find the AHC Motor Relay in the engine bay fuse box and test using the procedure at Page DI-243 (DTC1741) in the FSM extract attached to Post #952 in this thread,

7. Pull and replace (renew if necessary) the 15 amp AHC B fuse and the 20 amp AHC IG fuse. These fuses are not in the engine bay but are located in one or other of the junction panels behind the kickpanels in the footwell forward of the front doors – not sure on which side in your model, expect LHS. The purpose here is to be sure of the condition of these fuses, and also to power OFF the AHC Main Relay (this is different to the AHC Motor Relay in the engine bay fuse box) and also power OFF the ECU – in effect “rebooting” these devices which may be enough to clear a fault. Disconnecting the battery for a few minutes should have the same “rebooting” effect – but it is better to physically check and test relays and fuses,

8. Test the operation of the AHC Main Relay – this is mounted on the Electronic Control Unit (ECU) -- see location at Page DI-217 in the FSM extract attached to Post #952 and test details at Page DI-248 (C1743). The purpose is to ascertain whether this Relay is working -- see also pictures at Post #914 in this thread – if not, then no power is delivered to the ECU nor other sensors and controls in the AHC system and the AHC system cannot work,

9. Test the AHC Pump by direct connection to a 12 volt source, either directly at the pump connection or by pulling the AHC Motor Relay and using the terminals in its socket. Disconnect the hydraulic line from the pump or lower down at the Attenuator to see whether the Pump appears to be developing strong pressure and flow. This can be messy -- have a container in place to catch fluid discharged by the Pump. The purpose is ascertain whether

-- the AHC Pump is capable of operation if not inhibited by faults in the AHC system which prevent AHC operation, AND,

-- the pump develops strong pressure and flow, OR,

-- weak pressure and flow might suggest a full or partial blockage at the filters/strainers inside the Pump.

Be aware that upwards and downwards AHC movements of the vehicle are controlled by the Levelling Valves within the Control Valve Assembly. These valves are “NORMALLY CLOSED”. If the AHC system is not working or is in ‘fail-safe mode’, then these valves will not open, they will remain closed. In answer to one of your questions, if the AHC system is not working, then pressure from the AHC Pump by direct 12 volt connection WILL NOT result in flow at an open bleeder because the Levelling Valves are closed,

10. If the problem has not been discovered, first review all of system using the “Problems Symptoms Table” at Page DI-221 in the FSM extract attached to Post #952 in this thread. Where suspicions arise, this may lead to a review of the relevant individual circuits (see pages DI-224 to Pages DI-309). In answer to your question, note that there are multiple fault conditions (specified in the notes on individual circuits) which may result in ‘fail-safe function’ and prohibit the operation of the AHC system,

11. If the problem still has not been discovered, it is time to use a multi-meter, maybe with the help of an electrically-minded friend, and check ALL of the voltages at the AHC Electronic Control Unit (ECU), as shown at Pages DI-218 to DI-220 in the FSM extract attached to Post #952 in this thread. The purpose is reveal a possible problem with the ECU itself, and also the more likely possibilities of problems in the wiring harness and various connectors. This is an arduous task. Before commencing, it is worthwhile to read through all the Posts in the thread by @YvesNL at the following link:

Hi From The Netherlands & AHC Issues - https://forum.ih8mud.com/threads/hi-from-the-netherlands-ahc-issues.997849/

++++++++

A “BDC 2 Diagnostic test” is mentioned at your Post #937 in this thread. I am not sure what is meant by this description – and in any case I do not know how to interpret the “blinking code”.

At your Post #936 in this thread, you have asked:

“What is the precise journey of the fluid? ie, from AHC pump to "???" and from "???2" to and from "???3" to ect ect
Does the fluid from the AHC leave the AHC and go to the longish barrel shape Accumulator first, ( on my RHS chassis rail between the rear and front globes) or does it go to the Levelling Manifold before going to the main accumulator?”

When the Height Control Accumulator is empty (or not functioning properly), the AHC Pump will slowly raise the vehicle to the height controlled by the Height Control Sensors and Height Control switch on the centre console PROVIDED THAT the AHC system is working properly and the ECU has caused the Levelling Valves (in the Control Valve Assembly) to open. This allows fluid to flow to the ‘shock absorbers’ and raise the vehicle (see also paragraph 9 above). After the vehicle has arrived at the required height (and the green AHC light has stopped blinking), then the ECU causes the Levelling Valves to close, and also causes the solenoid valve at the front of the Height Control Accumulator to open. The AHC Pump then will re-fill the Height Control Accumulator in readiness for the next ‘raise’.

If the Height Control Accumulator already is full and working properly, the ECU will cause the solenoid valve at the front of the Height Control Accumulator to open and cause the Height Control Accumulator to discharge first when the vehicle is being raised and the vehicle will raise more quickly. This is the only purpose of the Height Control Accumulator. If necessary, the AHC Pump may complete the ‘raise’. Again, after the vehicle has arrived at the required height (and the green AHC light has stopped blinking), then the ECU causes the Levelling Valves to close, and also causes the solenoid valve at the front of the Height Control Accumulator to re-open. The AHC Pump then will re-fill the Height Control Accumulator in readiness for the next ‘raise’.

“The precise journey of the fluid” is shown under various different conditions in the hydraulic circuit diagrams in the last few pages of the PDF document “AHC General Description” attached below to this Post. This 20 page document is recommended for printing and study. It gives a very good description with many diagrams of how the AHC and TEMS systems and their components are meant to work on LC100 and LX470 vehicles.

Hope that your vehicle has more simple issues which are more easily resolved than some of the ideas mentioned above!!

Maybe other IH8MUD Members can cut through with quicker and more direct ideas from their knowledge and instincts?

 

[Urtwob]

Good evening @Urtwob

You have acknowledged that

“…. operating via manual testing without a Handheld computer such as Techstream, is a serious handicap”.

This definitely is very true – and you understand that -- but it is still worthwhile to attempt some diagnosis based on the physical symptoms observed without the hints given by DTC’s observable on Techstream.

It also means the Front and Rear AHC pressures are unknown unless they have been physically measured recently with pressure gauges.

With no passengers, no load and full fuel tank(s), Front AHC pressure (by Techstream) should be in the range 6.4 Mpa to 7.4 Mpa and Rear AHC pressures (by Techstream) should be in the range 5.9 Mpa to 7.0 Mpa (assuming that you have the additional fuel sub-tank, otherwise a little lower). These numbers are approximately 1.2 Mpa higher when measured with pressure gauges as defined in the FSM in the “On-vehicle Inspection” section. See more details at:

LC100 Workshop Manual - https://lc100e.github.io/
then tabs in the left hand panel of the opening page:
Repair Manual > SUSPENSION AND AXLE > ACTIVE HEIGHT CONTROL SYSTEM > ON-VEHICLE INSPECTION

Is this a simple matter of unknown AHC pressures being excessive, causing the ECU to stop the AHC Pump??

This is possible but seems unlikely. It is clear from your description that the AHC pressures are negligible at the moment – they are nothing like the above numbers – confirmed simply by your observation that there is no flow when the bleeders are open, with or without the AHC Pump running, and with the vehicle at or near the bump-stops.

If an AHC over-pressure problem is suspected but cannot be measured, then this idea could be tested by supporting part of the weight of the vehicle on jacks, or transferring more weight to the front torsion bars (wind say five turns clockwise at the torsion bar adjusters to reduce Front AHC pressures by ~1 Mpa), then seeing whether the AHC system will operate at lesser load and pressures.

Otherwise, AHC pressures can be addressed later.

The first order of business is to discover

(1) why the AHC Pump does not run under the control of the AHC Electronic Control Unit (ECU), and also

(2) what faults are indicated by the AHC Pump not running when the ECU is by-passed using the “Active Test”.

Given all that has gone before in the previous posts, and noting that the diagnosis must proceed without Techstream or other scanner capable of reading AHC Diagnostic Trouble Codes (DTC’s) and must rely only on observed physical conditions, may I suggest the following sequence?

Some of this may already have been done – the sequence is expressed this way simply for completeness and to provide a list of items that can be ‘ticked off’ in a sequence going from ‘simple’ to ‘complicated’ in an effort to find why the AHC system is not working and to allow remediation of the problem:

1. Check that all connections at the AHC Pump and Motor are seated and tight, with connectors and harness wiring in good condition (power to Pump, connector to Pressure Sensor, connection to Temperature Sensor. The purpose is to eliminate simple problems first,

2. Test the condition of the pressure sensor next to the AHC Pump using the procedure at Page DI-219 (DTC 1718) in the FSM extract attached to Post #932 in this thread. The purpose is to be sure of the condition of the Pressure Sensor – the AHC system will not operate if it is faulty,

3. Delete all existing DTC’s and fault conditions manually using the procedure below at DLC1 in the engine bay (connect E1 and Tc) or the equivalent FSM procedure using DLC3 (Tc to CG) under the dash. Special Service Tool SST 09843-18020 and 09843-18040 are a simple wire connectors – instead suggest use an unbent paperclip or similar. The purpose is to reduce confusion by clearing DTC’s which may have arisen from previous work and which now may be irrelevant – such as when connecting and reconnecting components. The ongoing DTC’s and fault conditions will be re-established as soon as the engine is started. (Remove paperclip or other connector when finished and hold down for a few seconds the AHC “OFF” switch on centre console to re-start AHC system).

View attachment 2973167

4. Perform and make written notes of ALL the “Pre-check” tests exactly as described in the attachment at Post #895 in this thread using DLC1 in the engine bay, or, the equivalent procedure using DLC3 (Tc to CG) under the dash (FSM Page DI-208), meaning ALL of

(1) DIAGNOSIS SYSTEM CHECK, and then,

(2) INPUT SIGNAL CHECK (TEST MODE CHECK), and then,

(3) DTC OF INPUT SIGNAL CHECK, and then,

(4) DAMPING FORCE CONTROLLING CONDITION CHECK, and then,

(5) HEIGHT CONTROL OPERATION CHECK (ACTIVE TEST),

and in each case being sure of the correct connections, using a simple connector such as an unbent paperclip or similar and with all doors and tailgate closed, interior lights OFF, aircon OFF, other ancilliaries OFF, steering straight ahead. The purpose is to begin the diagnosis process systematically (as a Doctor would with the human body) rather than starting with premature guesses. Then ascertain what works and what is inhibited in some way. (Again, remove paperclip or other connector when finished and hold down for a few seconds the AHC “OFF” switch on centre console to re-start AHC system).

By the way, when the instructions for the above tests in the referenced attachment or in the FSM say “Turn the ignition switch ON”, it actually means “START the engine”,

5. Given your previous observations and notes, it is possible that some, or even many, of these “Pre-check” Tests are negative (do not produce a result) and if so, that is important information to record. The purpose is to try and work out what a logical continuing process might be – a sensible process of elimination, if you like,

6. Find the AHC Motor Relay in the engine bay fuse box and test using the procedure at Page DI-243 (DTC1741) in the FSM extract attached to Post #952 in this thread,

View attachment 2973168


7. Pull and replace (renew if necessary) the 15 amp AHC B fuse and the 20 amp AHC IG fuse. These fuses are not in the engine bay but are located in one or other of the junction panels behind the kickpanels in the footwell forward of the front doors – not sure on which side in your model, expect LHS. The purpose here is to be sure of the condition of these fuses, and also to power OFF the AHC Main Relay (this is different to the AHC Motor Relay in the engine bay fuse box) and also power OFF the ECU – in effect “rebooting” these devices which may be enough to clear a fault. Disconnecting the battery for a few minutes should have the same “rebooting” effect – but it is better to physically check and test relays and fuses,

View attachment 2973169

8. Test the operation of the AHC Main Relay – this is mounted on the Electronic Control Unit (ECU) -- see location at Page DI-217 in the FSM extract attached to Post #952 and test details at Page DI-248 (C1743). The purpose is to ascertain whether this Relay is working -- see also pictures at Post #914 in this thread – if not, then no power is delivered to the ECU nor other sensors and controls in the AHC system and the AHC system cannot work,

View attachment 2973170

9. Test the AHC Pump by direct connection to a 12 volt source, either directly at the pump connection or by pulling the AHC Motor Relay and using the terminals in its socket. Disconnect the hydraulic line from the pump or lower down at the Attenuator to see whether the Pump appears to be developing strong pressure and flow. This can be messy -- have a container in place to catch fluid discharged by the Pump. The purpose is ascertain whether

-- the AHC Pump is capable of operation if not inhibited by faults in the AHC system which prevent AHC operation, AND,

-- the pump develops strong pressure and flow, OR,

-- weak pressure and flow might suggest a full or partial blockage at the filters/strainers inside the Pump.

Be aware that upwards and downwards AHC movements of the vehicle are controlled by the Levelling Valves within the Control Valve Assembly. These valves are “NORMALLY CLOSED”. If the AHC system is not working or is in ‘fail-safe mode’, then these valves will not open, they will remain closed. In answer to one of your questions, if the AHC system is not working, then pressure from the AHC Pump by direct 12 volt connection WILL NOT result in flow at an open bleeder because the Levelling Valves are closed,

10. If the problem has not been discovered, first review all of system using the “Problems Symptoms Table” at Page DI-221 in the FSM extract attached to Post #952 in this thread. Where suspicions arise, this may lead to a review of the relevant individual circuits (see pages DI-224 to Pages DI-309). In answer to your question, note that there are multiple fault conditions (specified in the notes on individual circuits) which may result in ‘fail-safe function’ and prohibit the operation of the AHC system,

11. If the problem still has not been discovered, it is time to use a multi-meter, maybe with the help of an electrically-minded friend, and check ALL of the voltages at the AHC Electronic Control Unit (ECU), as shown at Pages DI-218 to DI-220 in the FSM extract attached to Post #952 in this thread. The purpose is reveal a possible problem with the ECU itself, and also the more likely possibilities of problems in the wiring harness and various connectors. This is an arduous task. Before commencing, it is worthwhile to read through all the Posts in the thread by @YvesNL at the following link:

Hi From The Netherlands & AHC Issues - https://forum.ih8mud.com/threads/hi-from-the-netherlands-ahc-issues.997849/

++++++++

A “BDC 2 Diagnostic test” is mentioned at your Post #937 in this thread. I am not sure what is meant by this description – and in any case I do not know how to interpret the “blinking code”.

At your Post #936 in this thread, you have asked:

“What is the precise journey of the fluid? ie, from AHC pump to "???" and from "???2" to and from "???3" to ect ect
Does the fluid from the AHC leave the AHC and go to the longish barrel shape Accumulator first, ( on my RHS chassis rail between the rear and front globes) or does it go to the Levelling Manifold before going to the main accumulator?”

When the Height Control Accumulator is empty (or not functioning properly), the AHC Pump will slowly raise the vehicle to the height controlled by the Height Control Sensors and Height Control switch on the centre console PROVIDED THAT the AHC system is working properly and the ECU has caused the Levelling Valves (in the Control Valve Assembly) to open. This allows fluid to flow to the ‘shock absorbers’ and raise the vehicle (see also paragraph 9 above). After the vehicle has arrived at the required height (and the green AHC light has stopped blinking), then the ECU causes the Levelling Valves to close, and also causes the solenoid valve at the front of the Height Control Accumulator to open. The AHC Pump then will re-fill the Height Control Accumulator in readiness for the next ‘raise’.

If the Height Control Accumulator already is full and working properly, the ECU will cause the solenoid valve at the front of the Height Control Accumulator to open and cause the Height Control Accumulator to discharge first when the vehicle is being raised and the vehicle will raise more quickly. This is the only purpose of the Height Control Accumulator. If necessary, the AHC Pump may complete the ‘raise’. Again, after the vehicle has arrived at the required height (and the green AHC light has stopped blinking), then the ECU causes the Levelling Valves to close, and also causes the solenoid valve at the front of the Height Control Accumulator to re-open. The AHC Pump then will re-fill the Height Control Accumulator in readiness for the next ‘raise’.

“The precise journey of the fluid” is shown under various different conditions in the hydraulic circuit diagrams in the last few pages of the PDF document “AHC General Description” attached below to this Post. This 20 page document is recommended for printing and study. It gives a very good description with many diagrams of how the AHC and TEMS systems and their components are meant to work on LC100 and LX470 vehicles.

Hope that your vehicle has more simple issues which are more easily resolved than some of the ideas mentioned above!!

Maybe other IH8MUD Members can cut through with quicker and more direct ideas from their knowledge and instincts?

HI Indrocruise

Thank you for another highly thought reply.

I was out working at the cruiser last night before i received your above reply
I apologise to everyone for my inconsistent approach. I have Fibroyamalgia and i find working on the cruiser very difficult.
Regardless, as a result of a number of observances last night i came to the conclusion that my AHC Pump might be blocked. So i took about taking it off the cruiser today and disassembled it.

Oh boy,
The Bell housing that the oil temperature probe fits onto at the back of the pump body assembly was full of a thick gunge black substance. I opened the pump more and found that this Gunk was inside the main pump body just before the small gear wheels.

i have not taken the pump any further apart.

i have a few questions,
Q, Is there any filter in the pump body assembly?
i have not found any filter as yet.
If there is no filter i have a great fear that some of this Gunk may have travelled on into the AHC system.
Is this possible, i really hope not as that gunk would not do any of the valve control system any good, or any of the solenoids.

It is like a slimey watery but very black substance and i feel small elements of sand like grime in the gunk.

Can anyone advise if there is any filtering system to prevent garbage getting out through the pump?

Q, Has anyone an exploded parts picture for the pump?
Their must be more than one pump type as i have just watched a pump disassembled on youtube and there are difference between that pump and mine.

My cCruiser is a 1998 LC100 VX

Any help, pictures or and rebuild instructions would be most welcome.

I must bury my pride and admit again that after my rear AHC strut / shock absorber / Ram, burst, i was a very foolish person in that i did drive on using the cruiser on the bump stops for nearly a month. What i didn't do was have the brains to instantly disable the AHC.
I should of taken out the 50a fuse and the AHC relays so as to kill the system. If i had of done this the remaining Ahc fluid would of been retained in the reservoir and the drying out and clearing out of the bottom of my AHC reservoir would not have happened and therefore it would not of permitted this gunk to get into the system. I suspect if i had disabled the system, regardless of whether i used the cruiser or not, when i fitted my two new struts / rams and two new springs, the only other bother i would of had was a straight forward bleeding of the system.
i am convinced it was absolutely my stupidity that has caused the nightmare i have been having.

That all said, as Indrocruise has said more than once, we are where we are, so we will try and progress logically from this point.

I am not sure if my pump is damaged, it appears that it has never been run bone dry even if it is this gunge that is in there.

Interestingly as i disassembled the pump i could see signs or traces of water globules separating from the other gunge.

Let me remind everyone of the sequence of events,
Burst strut
Continued on driving
AHC OFF light did not blink in first week but i knew the oil had escaped.
i had another half jar 2.5 ltr of genuine ahc oil
i put it into reservoir when i saw it was looking empty.
but almost immediately the AHC Off light came on

It was here that i became even more stupid, i thought it was ok to drive on as the AHC OFF light was on so therefore the system was no longer active.

a few weeks later i received my new struts and springs and they were fitted immediately.

I am going over all of this sequence to illustrate that there was the strong possibility of the reservoir emptying out, and then the remaining oil and slime lying in the bottom of the tank possibly was dried out to a skin like substance because of the heat from the working engine. Then i put in the next 2.5 ltr of oil, but the AHC was immediately into off mode, then after the new parts came we filled with new AHC oil, however the reservoir was bone dry again despite the AHC OFF light being on since the 2.5 ltr of oil was put in.

Well, have i convinced everyone i have been a right idiot over this whole journey!!!
Regardless of when AHC OFF light came on, and especially as i had no option but to continue using the vehicle, i should of disabled the system from the primary instance of the burst, period.

I am going to open a few hex head studs i see in the pump body block. and i think i will disassemble the electric motor from the block as well, just to both check for any more trouble or and to educate myself as to the complete disassembly of the whole pump.

As mentioned i would really appreciate any and all exploded drawings, and parts descriptions as well as any hints on how i could detect if any other gear wheels or the inner tolerances have been irreparably damaged.

Thank you to everyone for you continued assistance.

 

[IndroCruise]

HI Indrocruise

Thank you for another highly thought reply.

I was out working at the cruiser last night before i received your above reply
I apologise to everyone for my inconsistent approach. I have Fibroyamalgia and i find working on the cruiser very difficult.
Regardless, as a result of a number of observances last night i came to the conclusion that my AHC Pump might be blocked. So i took about taking it off the cruiser today and disassembled it.

Oh boy,
The Bell housing that the oil temperature probe fits onto at the back of the pump body assembly was full of a thick gunge black substance. I opened the pump more and found that this Gunk was inside the main pump body just before the small gear wheels.

i have not taken the pump any further apart.

i have a few questions,
Q, Is there any filter in the pump body assembly?
i have not found any filter as yet.
If there is no filter i have a great fear that some of this Gunk may have travelled on into the AHC system.
Is this possible, i really hope not as that gunk would not do any of the valve control system any good, or any of the solenoids.

It is like a slimey watery but very black substance and i feel small elements of sand like grime in the gunk.

Can anyone advise if there is any filtering system to prevent garbage getting out through the pump?

Q, Has anyone an exploded parts picture for the pump?
Their must be more than one pump type as i have just watched a pump disassembled on youtube and there are difference between that pump and mine.

My cCruiser is a 1998 LC100 VX

Any help, pictures or and rebuild instructions would be most welcome.

I must bury my pride and admit again that after my rear AHC strut / shock absorber / Ram, burst, i was a very foolish person in that i did drive on using the cruiser on the bump stops for nearly a month. What i didn't do was have the brains to instantly disable the AHC.
I should of taken out the 50a fuse and the AHC relays so as to kill the system. If i had of done this the remaining Ahc fluid would of been retained in the reservoir and the drying out and clearing out of the bottom of my AHC reservoir would not have happened and therefore it would not of permitted this gunk to get into the system. I suspect if i had disabled the system, regardless of whether i used the cruiser or not, when i fitted my two new struts / rams and two new springs, the only other bother i would of had was a straight forward bleeding of the system.
i am convinced it was absolutely my stupidity that has caused the nightmare i have been having.

That all said, as Indrocruise has said more than once, we are where we are, so we will try and progress logically from this point.

I am not sure if my pump is damaged, it appears that it has never been run bone dry even if it is this gunge that is in there.

Interestingly as i disassembled the pump i could see signs or traces of water globules separating from the other gunge.

Let me remind everyone of the sequence of events,
Burst strut
Continued on driving
AHC OFF light did not blink in first week but i knew the oil had escaped.
i had another half jar 2.5 ltr of genuine ahc oil
i put it into reservoir when i saw it was looking empty.
but almost immediately the AHC Off light came on

It was here that i became even more stupid, i thought it was ok to drive on as the AHC OFF light was on so therefore the system was no longer active.

a few weeks later i received my new struts and springs and they were fitted immediately.

I am going over all of this sequence to illustrate that there was the strong possibility of the reservoir emptying out, and then the remaining oil and slime lying in the bottom of the tank possibly was dried out to a skin like substance because of the heat from the working engine. Then i put in the next 2.5 ltr of oil, but the AHC was immediately into off mode, then after the new parts came we filled with new AHC oil, however the reservoir was bone dry again despite the AHC OFF light being on since the 2.5 ltr of oil was put in.

Well, have i convinced everyone i have been a right idiot over this whole journey!!!
Regardless of when AHC OFF light came on, and especially as i had no option but to continue using the vehicle, i should of disabled the system from the primary instance of the burst, period.

I am going to open a few hex head studs i see in the pump body block. and i think i will disassemble the electric motor from the block as well, just to both check for any more trouble or and to educate myself as to the complete disassembly of the whole pump.

As mentioned i would really appreciate any and all exploded drawings, and parts descriptions as well as any hints on how i could detect if any other gear wheels or the inner tolerances have been irreparably damaged.

Thank you to everyone for you continued assistance.

Late edit: Pictures added at end of message

Well, it seems like you have made a discovery!! No need or point in beating up on yourself -- we all learned about the AHC system by doing, with 'hands-on', and with plenty of 'educational' mistakes along the way! Press on!

The AHC system looks after itself quite well -- some would say too well, because diagnosis sometimes can be quite baffling! The positive is that if your AHC Pump has run low on fluid, the Pump will simply stop -- due to one or more of the so-called 'fail-safe functions', in this case initiated by the Pressure Sensor sensing low internal pressure and the ECU causing the Pump to stop very quickly -- see details at page DI-229 (for C1718), page DI-252 (for C1751) and most importantly page DI-257 (for C1762) in the "Diagnostic" extract from the FSM, provided at Post #952 in this thread.

The Pump will not run when it is dry. At this point the AHC actions are prohibited by the system. The AHC system is no longer active.

The "Active Test" is the FSM-prescribed procedure to restart (actually prime) a stopped Pump, and allow the AHC system to be re-pressurised.

The fact that the "Active Test" does not work on your vehicle is indicative of several possible problems -- of which AHC Pump blockage is one possibility, foreshadowed as “Alternative #2” back at Post #908 in this thread and in related posts by @2001LC.

May I say that the accumulation of debris in the housing around the AHC Pump is not surprising in a 24 years old vehicle. This is one of the known accumulation places – the other common accumulation places are in the ‘shock absorbers’. Materials which lodge in these places can be difficult to shift, because AHC Fluid does not really circulate but just goes backwards and forwards when the system is operating.

The best approach to ‘hydraulic hygiene’ is to change out the AHC Fluid frequently – evacuate the AHC tank and discard the fluid, replace with new AHC Fluid, then carry out long bleeds with new AHC Fluid at all five (5) bleeding points until new, clean bubble-free fluid is observed. This will not be perfect because a straight-through complete flush is not possible on the AHC system and some residue will remain – which is even more reason to do this frequently.

At the same time, it is wise to replace all five (5) bleeder valves and all (5) protective caps on the bleeder valves. The cost of replacement is tiny. The cost and inconvenience of dealing with old bleeders frozen with rust is HUGE.

In my personal opinion, the fluid changeout should be done at least every three (3) years. My recollection is that the Owner’s Manual recommends every six (6) years or every 60,000 miles (100,000 kilometres) – too far apart for me!

The fluid used must be only genuine Toyota/Lexus AHC Fluid, such as international Toyota/Lexus Part Number 08886-01805, supplied in 2.5 litre steel drums and manufactured by Japanese oil company Idemitsu Kosan Co., Ltd, or, it may come in different packaging with a different Part Number in some markets. Use of other fluids, such as brake fluid, auto transmission fluid, steering fluid, invites complete disaster by degrading seals and membranes, thereby reducing the life of ‘globes’ and seals and increasing debris and increasing blockage risks in the AHC system.

Recently, you have replaced ‘globes’ and ‘shock absorbers’. This would have involved bleeding of a lot of fluid, so unless incorrect fluid was used or old dirty fluid was recycled, the AHC Fluid in your system should be quite good – but obviously it has not ‘flushed out’ the accumulation you have discovered.

Following below are some informative links to background information and pictures of Pump internals, including the only diagram of the AHC Pump internals to be found in the Factory Service Manual (FSM), together with information about the screens/strainers within the AHC Pump ....

Previously, @PADDO made observations at Posts #16 and #19 in the thread below:

AHC help needed

I hooked my 2002 LX470 with 80K miles up to techstream yesterday to see what my neutral pressure readings were after replacing my globes. I was only getting like 6 graduations from the old globes and my front suspension felt like it was stuck in sport mode. After replacing the globes I have...

forum.ih8mud.com

At this post #19 in the above link, it is noted that:

“The two screens are internal to the pump so the pump/reservoir assembly needs to be removed from the vehicle. It’s then a matter of taking off the circular external pump housing which gives access to the pump. It’s retained to the main body and held together, its a sandwich design, by four cap screws. Undo the screws, and disassemble the pump sandwich and the screens are revealed. They are pressed in and can be cleaned in situ with a blast of 100% hydrocarbon cleaner or you can back them out with a pick to clean. Reassemble, install the pump/reservoir fill with fluid and let it sit for a while to assist the fluid in working it’s way into the pump housing/intake and fire it up. If it times out because it’s airlocked and can’t prime then force run it manually**”.

* in other words, something that dissolves oils and evaporates readily without leaving a residue, so not a detergent.

** means operation of the pump by “Active Test” for about 10 seconds with AHC fluid at correct level or better in the tank, or operation by direct connection of the pump motor to the battery.

My further notes: If a clean-up is being done, it is worth disassembly of the pump to investigate the screens/strainers which are are located inside the actual pump itself, on the input and output sides of the tiny gears (smaller than a thumbnail) which provide the actual pumping action. Gear pumps usually are specified for high pressure / low volume applications where the fluid is free of particulates. The screens/strainers are intended to keep particulates out of the actual pump. Particulates might otherwise degrade or destroy the gear action.

When an AHC Pump is thought to have failed or a relevant DTC such as C1762 is recorded – meaning that the delivered pressure is too high or too low and AHC response is slow – this may have been caused by clogged screens/strainers rather than problems in the actual pump, unless the screens are missing or have holes which allow particles to pass into the gears. The pump is small but fit for purpose -- it would take something like a stream of sand to destroy the pump.

Many pictures of the Pump internals including the screens/strainers are found in Post #67 through to Post #70 in this next link and include my pictures of disassembly of my AHC Pump:

AHC pump out? With code 1762

I have seen 1.x was able to program key, customize telescoping, door lock, window and sunroof settings. The 1.x cable I own was able to program my key, disable my DRLs, and stop that annoying auto-telescope wheel from activating. I have a 01LX that doesn't have TPMS, and I have read multiple...

forum.ih8mud.com

The problematic internal strainers/screens (not to be confused with the strainer at the AHC Tank) are shown at Post #70 in the above thread.

The main purpose of the pump cover with the big "+" on the outside is to contain the pressure which is used to force the pump gears tightly onto the pump body so as to minimise side clearances and minimise fluid bypassing the gears at their sides. There won't be much flow in the space inside this cover but outside the actual pump. It is a natural trap for fluid.

As for many types of oils warmed and cooled over a long period of time in the presence of oxygen and moisture, a gel or sludge eventually will form in traps where fluid is stationary or moves slowly. Some of this gel or sludge may find its way into the pump. If so, it will be caught at the internal screens/strainers inside the pump along with any accumulation of particulates not fine enough to pass through the screens/strainers. The pressure drop across the wholly or partially blocked screens/strainers will cause a loss of pump output pressure and flow.

So a clean-out is a good idea when there are suspicions about pump delivered pressure and flow being low and/or DTC C1762.

A source of replacement internal screens/strainers is not known -- they are not detailed in the FSM and do not appear on commonly available parts diagrams and lists and are not shown on Toyota/Lexus lists. It is not known which of the many suppliers to Toyota/Lexus factories is the actual manufacturer of the AHC Pump. It is suspected that it might be KYB who make the Height Control Accumulator used on LC100/LX470. The FSM deals with the issue only by recommending replacement of the AHC Pump rather than repair.

The screens/strainers could be eased out with a pick as mentioned by @PADDO -- but carefully, do not want any holes in the mesh. A simple backwash may be a safer approach.

Alternatively, and for peace of mind, replacing the pump sub-unit every 15 to 20 years (or 24 years!) may not be such a bad idea – especially where long term neglect (infrequent AHC fluid changes and infrequent AHC pressure checks) by previous owners is suspected. The pump sub-unit is Part Number 48901-60010 – current price example: Partsouq: USD168.19 plus delivery.

Suggest if disassembling the pump to clean the internal screens/strainers, then either leave the tiny gears and their carriers in place, or, carefully mark and photograph their orientation to one another so that all parts can go back together with parts and gears oriented and meshing in exactly the same way. Otherwise, the Pump may not work at all. Ideally, replace all o-rings encountered and also the oil seal between the pump and the motor and the grommet between the AHC Tank and the AHC Pump.

Suggest if using a secondhand pump, disassemble and clean the screens/strainers and inspect the gears before installing in the vehicle.

Also suggest bench testing the overall Pump/Motor assembly with a direct 12 volt supply before reinstalling it in the vehicle.

For better peace of mind, suggest consider replacing the AHC Pump with a new Pump (not the whole assembly of Pump, Sensors, Motor, Tank -- just the Pump). The motor driving the pump is a very long-life unit -- you may wish to disassemble to inspect the bearings and brushes etc, although it is worth being aware that there are few if any reports on IH8MUD of failure of this motor.

Suggested purchases:

48901-60010 – AHC Pump,
90301-70003 – large O-ring for AHC Pump,
90301-06012 – small O-ring for AHC Pump,
47255-60010 – grommet between AHC Tank and AHC Pump,
49189-60010 – replacement bleeder valves (5 required),
49177-60010 – replacement bleeder caps (5 required),
08886-01805 – AHC Fluid in 2.5 litre steel drums, at least two, probably three drums,

Probably, around USD200 in total for new OEM units in the above list, delivered from the overseas suppliers, such as Toyota | Parts Catalogs | PartSouq - https://partsouq.com/en/catalog/genuine/locate?c=Toyota. Partsouq is used by many IH8MUD Members including me, unless local Toyota/Lexus dealers can come close to the prices found on the Partsouq catalogue + delivery etc. Prices in various currencies and delivery costs to different locations around the world can be found on this website without obligation to buy.

Some visuals of actual disassembly of an AHC Pump internals, gears, etc, can be seen on Youtube. These often are not LC100/LX470 AHC Pump assemblies but instead are LC200 Pump assemblies -- these are distinguishable by the Attenuator (small brown cylindrical object) mounted next to the actual AHC Pump. The Attenuator is located separately below the AHC Pump on LC100/LX470. The LC200 AHC system is quite different -- and the tank, pump, motor etc are mounted in the RHS rear quarter panel behind the RHS rear wheel. The actual Pump internals on LC200 appear much the same (and may be exactly the same) as the LC100/LX470 Pump and the visuals give the idea. However, it is safest to rely on the pictures on the various IH8MUD "100 series" threads.

I don't mean to be pessimistic but it does appear that there may be multiple faults on your AHC system. The good news is that all parts of the AHC system definitely are repairable -- and at reasonable costs. One thing at a time -- today it is the AHC Pump!

Further down the track when the AHC system is working again and ready for adjustment, the video on Youtube prepared by @suprarx7nut a.k.a. AHC Info - https://www.yotamd.com/blogs/news/ahc-info is the "go to" video. By then, Techstream will be essential.




LC100/LX470 Pump disassembled (picture by @IndroCruise )

Strainer position -- enlarge to see insider strainer below brass ring (picture by @IndroCruise

Strainer position -- enlarge to see insider strainer below brass ring (picture by @IndroCruise )

Strainers removed and cleaned (picture by @Zel)

Overall layout of LC100/LX470 Assembly of Pump, Motor, Pressure Sensor, Temperature Sensor, Tank:

 

[Urtwob]

As usual IndroCruise
Your replies are Supreme.

I cannot think of appropriate ways to express my appreciation to the extent required.

Ok, I’ve a bit more study to do,
I will admit, after removing the four hex screws and lifting the “lid” off the pump itself, I still remained confused as to where these screens were located.

I have no doubt that within the above attachments you have just supplied I will come to a much better understanding.

I have made a bad mistake, I’m sure you are already suspicious of this, I did remove the gear assembly, but without marking to ensure “perfect” replacement, so I think it might be best to replace the pump.

My local Toyota supplier has quoted £436 Sterling plus 20% Tax, for the small pump assembly. So total of £523.20 Sterling, I personally think this is seriously excessive for this individual component. I will most certainly be contacting Partsouq to source this component.

However, being totally realistic, with the quantity of sludge discovered inside the “+” cap or chamber and the fact the vehicle is 24 years old, a new pump sub assembly is probably unavoidable regardless of my mistake. I have worked a little with pump gears before and I should of known better and made sure to prepare for perfect replacement of the gear wheels. Not making excuses but my pain threshold capacity had been well superceeded by the time I was taking the pump assembly apart thus mistakes were being made. I need to learn to “pace” myself better.
I’m an “older” guy still trying to believe I still have my youthful exuberance.

I have One final question as regards my current status, is it possible that I have forced or pushed some of this sludge through the pump and into the AHC system, by my unwitting use of the direct 12v supply and if so will this cause further difficulties?

At one point, with the Bleed screw open, and using the 12v direct method
I was having “a reasonable” quantity of AHC fluid being pumped through to the accumulator barrel and straight out the bleed screw, but eventually the pump became quieter and the volume of fluid dropped to a small dribble.
I did not abuse the 12v method in that I only ran it for approximately 10-15 second intervals. But the fact it developed into a dribble caused me further concern as I was suspicious I had unwittingly been forcing the pump to push the later discovered sludge through the system until it became naturally blocked even more thoroughly by my actions, ie, instead of making progress I was actually unwittingly packing the grime into the constricted orifices and screens even more so.

Truthfully, initially I though I was on to a good thing as in two or three instances of using this method, I found that when I went back to the cruiser and tried the normal operation of the AHC, the initial lighting sequence was normal and the vehicle sat with the green light flashing on the “N” position for up to 15 seconds before the “Off” light started blinking, (my son kept his hand on the pump and confirmed the motor was running until the off light switched on) Prior to this the “Off” light had come on immediate to initiating the normal procedure.

Now then, thanks to your continued efforts IndroCruise, I’m off for a bit more study of the supplied attachments.

Once again, thank you my friend.

 

[Urtwob]

As usual IndroCruise
Your replies are Supreme.

I cannot think of appropriate ways to express my appreciation to the extent required.

Ok, I’ve a bit more study to do,
I will admit, after removing the four hex screws and lifting the “lid” off the pump itself, I still remained confused as to where these screens were located.

I have no doubt that within the above attachments you have just supplied I will come to a much better understanding.

I have made a bad mistake, I’m sure you are already suspicious of this, I did remove the gear assembly, but without marking to ensure “perfect” replacement, so I think it might be best to replace the pump.

My local Toyota supplier has quoted £436 Sterling plus 20% Tax, for the small pump assembly. So total of £523.20 Sterling, I personally think this is seriously excessive for this individual component. I will most certainly be contacting Partsouq to source this component.

However, being totally realistic, with the quantity of sludge discovered inside the “+” cap or chamber and the fact the vehicle is 24 years old, a new pump sub assembly is probably unavoidable regardless of my mistake. I have worked a little with pump gears before and I should of known better and made sure to prepare for perfect replacement of the gear wheels. Not making excuses but my pain threshold capacity had been well superceeded by the time I was taking the pump assembly apart thus mistakes were being made. I need to learn to “pace” myself better.
I’m an “older” guy still trying to believe I still have my youthful exuberance.

I have One final question as regards my current status, is it possible that I have forced or pushed some of this sludge through the pump and into the AHC system, by my unwitting use of the direct 12v supply and if so will this cause further difficulties?

At one point, with the Bleed screw open, and using the 12v direct method
I was having “a reasonable” quantity of AHC fluid being pumped through to the accumulator barrel and straight out the bleed screw, but eventually the pump became quieter and the volume of fluid dropped to a small dribble.
I did not abuse the 12v method in that I only ran it for approximately 10-15 second intervals. But the fact it developed into a dribble caused me further concern as I was suspicious I had unwittingly been forcing the pump to push the later discovered sludge through the system until it became naturally blocked even more thoroughly by my actions, ie, instead of making progress I was actually unwittingly packing the grime into the constricted orifices and screens even more so.

Truthfully, initially I though I was on to a good thing as in two or three instances of using this method, I found that when I went back to the cruiser and tried the normal operation of the AHC, the initial lighting sequence was normal and the vehicle sat with the green light flashing on the “N” position for up to 15 seconds before the “Off” light started blinking, (my son kept his hand on the pump and confirmed the motor was running until the off light switched on) Prior to this the “Off” light had come on immediate to initiating the normal procedure.

Now then, thanks to your continued efforts IndroCruise, I’m off for a bit more study of the supplied attachments.

Once again, thank you my friend.

Good Night Indrocruise, (Irish Time) 22.43

Well I’m a very relieved chap my friends.

I have very good news !!
My cruiser AHC problem has been resolved.
“The Phoenix has Risen.”


I have been on quite a journey with my AHC system. I must admit i have found the whole process extremely educational and I truthfully enjoyed the process so far.
I am an out and out fan of the AHC system.

Yes being disabled I find the practical benefits of the system life changing, however it is truly the case that I believe the AHC system to be an awesome piece of mechanical engineering.

I have a genuine desire to understand the innermost workings of this system.

The Great News is, after approximately 4 months my Cruiser has Risen.

Boy what a feeling to observe those first tentative movements where you are doubting yourself as to whether it moved at all.

But then it becomes more and more obvious that the cruiser is definitely rising, like The Phoenix from the ashes. Granted I had to turn off / On and restart the cruiser a number of times.

I had a few very helpful posts from a number of forum members but in the interests of fairness I must at least mention Indrocruise who has been with me on this journey from start to finish.

I thank each and every member who contributed as we go along but a massive thanks must go to Indrocruise.

You are a Star, my friend, as far as we Irish are concerned
“Your The Man”

I know I have meandered from the totally rational logic route, onto the totally irrational illogical routes a few times but you have held to a courteous respectful and positive manner in every instance.
I would not be surprised to learn that you have been a person involved in education all your life.

But a great big Irish Thank you my friend and if you ever make your way to our small part of the globe there will be a very warm Irish welcome to you and your family.
It goes without saying that this welcome may involve our famous Bushmills Irish Whiskey as a starter not least because the Bushmills distillery is only a few miles from our home.

However,

What happened??

Going back a few weeks now I had installed a new set of rear struts and new rear springs.
(Also worth mentioning I have installed 4 new Gas Spheres or globes about 2 years ago)

However immediately after the recent installation of the struts the cruiser refused to rise.
( I must admit to not treating my cruiser very well as I continued to drive and work it for a few months before effecting the attempt at repairing it.

So Here I started my most recent journey with this amazing IH8MUD Forum and its wonderful members.

IndroCruise selfilessly and generously took to taking me step by step through the process, or indeed as it turned out, the processes as we had to embark on an alternative route when it became clear the “Active Test” was not going to work.

I am not going to go into every step here as it would be a very long story indeed.

After going through the steps as directed by IndroCruise I had in essence been through a vast array of testing including all relays and fuses, then the height sensors and then on to the ECU, itself.
But alas all to no avail, I had early in my recovery efforts tried the “reset all codes” and the “Active Test” stage followed by the 12volt direct powering of the AHC Pump.
Indeed I had reverted back to trying the 12volt direct approach again a few days back.

As you all have experienced time and time again, each time you try this or try that the vehicle invariably proceeds to display unexpected behaviours and “off the beaten track expected or anticipated results” which lead us to taking sometimes unexpected options due to some small happening within the system.

Two nights ago the AHC motor displayed somewhat unexpected behaviour in that in direct 12v mode it was pumping fluid straight through to the barrel accumulator and pumping the fluid straight out the bleed screw.

It continued to do this quite aggressively but despite going around the five bleed points at least five times, I could not get the cruiser to show any semblance of rising even slightly.

However, upon entering into another round of bleeding, I noticed the pump changing tone, to the extent I was genuinely worried I had destroyed the pump.
It became less and less aggressive and much much quieter.

Later that night upon reflection I got it into my head that perhaps the pump had actually got clogged or blocked up.

This focused my train of thought upon whether or not to take the AHC pump assembly apart to seek for sludge or any blockage.

The following morning I did just that,

It was surprisingly easier to get to the dissembled stage than I had anticipated, but alas I did make a few mistakes, the biggest one was not taking photographs of each stage and not carefully marking each component to ensure they were replaced precisely and exactly from where they had been removed.

In particular as IndroCruise highlighted the gear wheels would of most certainly been much better if the gears were dissembled in order to be replaced with the exact same gears meshing with each other, tooth by tooth.

However, I had to keep on moving despite these anomalies.

To my great pleasure I found quite a considerable volume of sludge inside the the pump housing End Cap. It is The End cap with the “Cross or plus sign on it”.

To my utter surprise and to be honest, delight I found there was approximately half of an egg cup full of sludge inside this End Cap. (The Temperature sensor is attached to This End Cap.

I used rubber gloves throughout this whole disassemble and reassemble. I continuously jetted the rubber gloves with the aerosol carbon cleaner to ensure the gloves were kept spotless.

I cleaned all components thoroughly before progressing on to disassembling the actual primary pump mechanism itself, the small module that holds the two gear wheels. I will call this assembly The Primary Pump Assembly.

Each and every part was washed and cleaned thoroughly.
Please forgive my crude methods but I found that using a spray can of aerosol carbon cleaner to spray and clean each component to a pristine shine.

I then embarked upon getting the two small filters removed. This was quite a job but boy was I glad I persevered.

May I at this stage once again thank Indrocruise for providing an extensive library of photographs and his detailed description of the pump being taken apart stage by stage.

May I also apologise for not taking photographs as I went through this process. I note how you professional contributors make great use of both photographs and video.
I will endeavour to progress to the use of photographs soon.

However These pictures supplied by Indrocruise are of immense help to anyone contemplating taking on this job.

These pictures are also extremely useful in understanding the following observations and suggestions as regards to rebuilding the AHC pump.

Now back to the Pump filters;

I tried quite a few methods to withdraw them from the housing, initially without success, in the end however I found that using as perfect a fit of wood screw was a perfect solution.
I ground off the point of the screw to prevent it from damaging the very small and very fine mesh of the filter.

I screwed the screw in very tentatively making sure not to go too far and when the screw had sufficient grip I extracted the screw and filter by mocking up a direct lift cantilever type affair that lifted the screw in a directly straight upwards trojectory. Once I got the “tensions” all as near as I could gauge this actually worked very well.

Now I have read in a few posts that some folk have suggested that due to the difficulty of extraction of these very petite and fragile filters, that they opted to not take them out but alternatively they jetted hydrocarbon cleaning fluid both directions from the inlet and outlet orifices.

I fully understand this decision, but upon my findings I don’t agree with trying to clean this way.

This was because I found it was very difficult to clean the small meshes in these petite filters when I had them totally removed from there enclosures never mind attempting to do so by simply blowing from either end of the enclosure.

I found that the debris which was a very fine sand like material was almost embedded like concrete inside the small mesh and to make it even more difficult these small meshes have small overlaps of mesh that must be gently manipulated by squeezing between your fingers to open up these small overlaps or flaps to ensure that all that dust like grain is removed.

It took me about 10 minutes to clean each of these filters thoroughly.
The degree of cleaning needed could not be achieved if the filters are not removed out of there receptacles or enclosures.

One of the filters was much more congested than the other.

I then took a very fine grade nail file and tidied up the top of the brass collar of the small mesh filter to ensure any scrapes or abrasions caused by my extraction were filed down smooth in readiness for reinsertion back into the respective orifices in the respective pump body parts.

When the pump body components are all thoroughly thoroughly cleaned ensuring that all the internal channels and journals are cleansed with certainty that the unseen portals or journals or oil-ways are absolutely spotlessly cleansed, then and only then the small filters must be reinserted.
I found it was necessary to press these small filters back into place.
I used vice grips with small pieces of rubber to protect the components from any damage.

This next stage is very very important,

The gear wheels and gear “axle” are a single unit with the gear wheel and the axle being milled as a single piece.

These axles fit into two small hubs that in turn press freely into the pump housing.

Here I made what could be a very significant observation,

There is a very petite cut-away or “Nick” machined out of the bottom edge of one of these hubs.

It is vital that these hubs are replaced hub by hub, back into the housing precisely back into the position they came out of.

Thankfully there are only two options or ways to instal these hubs into the housing.

For ease of explaining from here, let’s just say there is the right way and there is the wrong way.

However, installing the right way the fluid can flow unimpeded on its proper pathway,
However installing the wrong way, the pump cannot function as the aforementioned “nick” is in the wrong place thus the fluid cannot flow unimpeded.

I know I may be wrong here but so far I have never heard anyone mention this small “Nick” and boy is it not a vital part of the pumps mechanism. I have read and studies hundreds of posts as well as watched many videos but to date I have never heard of or been told to look out for this petite “Nick”.

Now as I admitted earlier I didn’t take notes or photograph indeed I took no actual records of the disassemble as I should have done.

Boy did I have a problem here,
“How do I know which way to re-instal these hubs”

In the end I did a miniature mock up of the assembly and using a fine nozzle and compressed air, I blew the air into the inlet hole on the housing, and indeed yes my first attempt was wrong as the air was not getting through. So now I knew to insert the hubs the alternative way.

So by the skin of my teeth I got past this hurdle.

I however could not get out of the next slip up so easily.

I hadn’t marked and recorded exactly where the teeth of the gear wheels met, tooth by tooth.
In this my friends I was defeated.
I had to proceed and hope that the pump would function for me with just a random guess with positioning the two gear wheels.

I wish to share another idea here if I may.

When I was assembling the components of the primary pump assembly I set up a very clean plastic jar in which I filled with AHC fluid.

I then set the components of the primary assembly into the AHC fluid and I assembled each component under the fluid ensuring each orifice was filled with AHC fluid from the onset of assembly.

This method also meant that all the components of the primary pump were assembled while submerged in the AHC fluid thereby ensuring that all the components were adequately lubricated as the assembly progressed.

Next step is to attach the Main Block of the pump to the primary pump module.
Being conscious of the need to avoid any and all air pockets I unscrewed the AHC Fluid pressure sensor out of the main block, filled the pressure switch orifice with AHC Fluid and then reinstated the AHC fluid pressure sensor back into the main block. I then set the “main block” on its side with the large End Cap O Ring looking straight upwards and the electric motor directly beneath sitting on the bench.

There is a second much smaller O Ring sitting inside the large O Ring, on this block face. It is vital this small o ring is kept in its place.

It is crucial to make sure it is kept in place. I believe this O Ring seals the faces of the two assemblies at the orifice that allows fluid access to the pressure sensor.

I filled AHC fluid into the upper face of this main block before dropping the primary pump assembly down into the block. Once again attempting to ensure that all orifices were filled with fluid and all joints lubricated.

There are a two other O RIngs who’s locations are obvious. However these two small O Rings have two small steel backing washers.
It is vital to replace these washers and O Rings precisely in the order they come of. However thankfully this is also intuitive in nature and can be worked out.
The washer and O Ring sit into a recess.
The washer goes into the orifice first, then the O Ring.

One other observation I made was that if you happen to slightly over tighten the primary pump assembly to the “main block” the pump will be too tight and the motor won’t be able to turn the gears in the gear Housing.

There are proper torque settings for tightening these four studs, but I couldn’t find them at the time.

So I just trusted in my experience and I lightly tightened each stud while at the same time I tested the motor by connecting to a 12volt battery, thereby being able to identify when I was coming closer to the “Sweet Spot”

Now the final “trick” I have to offer is as follows.

The final step of this stage is to attach The End Cap or housing, the black cap with three stud holes in which the primary pump assembly is housed. Or the black cap with the pressed “+” sign and with the temperature sensor attached.

Once again in an effort to ensure all orifices are filled with AHC Fluid, I got a large plastic dish.
The plastic dish was of a size that I could set the the End Cap upside down with the three protruding stud hole tags sitting on the edge of the plastic container.

I then filled the End Cap with AHC fluid.

Next I set the whole pump assembly down onto the end cap submerging the primary pump assembly into the AHC fluid once again in an effort to minimise any and all air pockets as the pump is assembled. The overflow of AHC fluid dropped cleanly into the plastic dish below thus saving it cleanly.

It is very important to make sure this dish is kept very clean so as to be able to reuse the overflowing AHC fluid.

I carefully inserted and tightened the three studs thereby sealing the End Cap onto the whole pump body.

All of the above “exercises” were conducted in an effort to ensure all the internal cavities of the pump were filled with clean AHC fluid and that all moving parts were adequately lubricated throughout the assembly.

And Finally,

I uncoupled the cruisers negative battery earths and didn’t refit for periods 20 minutes.

This was to attempt to rest the AHC ECU.

I then refitted the AHC FLUID reservoir on top of the pump. However I filled the reservoir receptor orifice with AHC fluid once again to attempt avoid any air pockets.
I then re installed the reservoir onto the pump.

I put some oil into the reservoir.

I re-installed the AHC pump assembly back into the cruiser. I re-joined the three plugs, the 12volt motor supply, the temperature sensor and the pressure sensor and the main AHC Fluid “out” line.

Then I half filled the reservoir with AHC Fluid.

I bled the outlet pipe again using the 12volt direct method, and then retightened the output pipe.

I then reconnected my battery negative terminals.

I wasn’t sure if I would need to use “The Active Test “ to get the pump going, indeed I still wasn’t sure if the pump would work.

To my great pleasure I noticed the AHC FLUID exiting the reservoir at quite a speed, and eventually after perhaps 2 or 3 ignition off / on and start engine again cycles.

And magically for the first time in over 3 months the front of the cruised began to rise. I had to keep cycling the ignition from on / off and restart a number of times and was delighted to See the rear of the vehicle rising.

I must admit I was very surprised that the cruiser lifted right up to its maximum height without any further bleeding.

I know i must bleed all the 5 points a few times tomorrow but
As it was now quite late here I decided to take the cruiser for a drive and I was of to bed.

It was absolutely wonderful being able to drive on bumpy and pot-holed roads without having to slow down to avoid the bumps and bangs, as I had to do for the past 3 months.

I realise I must bleed the system systematically tomorrow and hopefully I will get the front and rear heights sorted as well tomorrow.

One thing I noticed was that the cruiser was very fast in lifting from L to N and then from N to H.
I didn’t think of timing the rise but I believe it would be from Low to N in less than 10-15 seconds and the same from N to H.
However I don’t think it took anything near 30 seconds to get from L to H.

There are a few issues still needing sorted.

Although the cruiser lifted up to H, the green light AHC display only went up to N.
But when lowering, I press the down button once and the cruiser dropped a stage and the green light went down to L. However when I pressed the Down button again the cruiser drops down to the lower position.

I suspect two issues may be at play here,

1,
The rear height sensor is not adjusted correctly. I do remember moving it to a different position a few weeks back when I took the height sensors off the cruiser for testing.

2,
Given that I have installed new rear struts and new springs, it is highly possible the Torsion Bars will need adjusting.

But first I must bleed the system properly.

I can’t believe the cruiser actually managed to go from a complete pump rebuild to raising the cruiser to H without using Active Mode or without the AHC OFF light ever coming on.
I am also very pleased at how fast the cruiser raised up.

I cannot stress enough how difficult it was to clean the dust grit from between the flaps of the internal mesh filters mentioned above

In my opinion that grime in those flaps will cause a very high % loss of available through flow potential of AHC fluid going in or out of the AHC pump. The worst affected filter was the in-flow filter from the End Cap into the pump. Judging by the actual physical petite size I believe one could lose upwards on 80% of available fluid throughout.

I have no idea if my theory of reassembling the AHC pump while submerged in clean AHC fluid has had any specific benefit but I do know I am more than impressed how fast and efficiently this 24 year old pump has worked in the initial reinstating of the cruisers AHC from a complete cleanse and rebuild to what could be described as being in a “good” operational stare.

Albeit the system needs further refining and tidying up as mentioned above.

I know this is a long post, but I am writing it in the hope that someone will perhaps avoid certain mistakes and more importantly hopefully avoid the long lag time it took me to eventually find out what was wrong with my AHC system.

Thank you to all who contributed and a big thank you to Indrocruise for the meticulous directions and guidance which was presented in a totally non judgmental manner. I totally acknowledge I am a novice and I made quite a few mistakes as we went through this AHC recovery.

Now for a bit of shut eye, I hope.

 

[Urtwob]

Good Night Indrocruise, (Irish Time) 22.43

Well I’m a very relieved chap my friends.

I have very good news !!
My cruiser AHC problem has been resolved.
“The Phoenix has Risen.”


I have been on quite a journey with my AHC system. I must admit i have found the whole process extremely educational and I truthfully enjoyed the process so far.
I am an out and out fan of the AHC system.

Yes being disabled I find the practical benefits of the system life changing, however it is truly the case that I believe the AHC system to be an awesome piece of mechanical engineering.

I have a genuine desire to understand the innermost workings of this system.

The Great News is, after approximately 4 months my Cruiser has Risen.

Boy what a feeling to observe those first tentative movements where you are doubting yourself as to whether it moved at all.

But then it becomes more and more obvious that the cruiser is definitely rising, like The Phoenix from the ashes. Granted I had to turn off / On and restart the cruiser a number of times.

I had a few very helpful posts from a number of forum members but in the interests of fairness I must at least mention Indrocruise who has been with me on this journey from start to finish.

I thank each and every member who contributed as we go along but a massive thanks must go to Indrocruise.

You are a Star, my friend, as far as we Irish are concerned
“Your The Man”

I know I have meandered from the totally rational logic route, onto the totally irrational illogical routes a few times but you have held to a courteous respectful and positive manner in every instance.
I would not be surprised to learn that you have been a person involved in education all your life.

But a great big Irish Thank you my friend and if you ever make your way to our small part of the globe there will be a very warm Irish welcome to you and your family.
It goes without saying that this welcome may involve our famous Bushmills Irish Whiskey as a starter not least because the Bushmills distillery is only a few miles from our home.

However,

What happened??

Going back a few weeks now I had installed a new set of rear struts and new rear springs.
(Also worth mentioning I have installed 4 new Gas Spheres or globes about 2 years ago)

However immediately after the recent installation of the struts the cruiser refused to rise.
( I must admit to not treating my cruiser very well as I continued to drive and work it for a few months before effecting the attempt at repairing it.

So Here I started my most recent journey with this amazing IH8MUD Forum and its wonderful members.

IndroCruise selfilessly and generously took to taking me step by step through the process, or indeed as it turned out, the processes as we had to embark on an alternative route when it became clear the “Active Test” was not going to work.

I am not going to go into every step here as it would be a very long story indeed.

After going through the steps as directed by IndroCruise I had in essence been through a vast array of testing including all relays and fuses, then the height sensors and then on to the ECU, itself.
But alas all to no avail, I had early in my recovery efforts tried the “reset all codes” and the “Active Test” stage followed by the 12volt direct powering of the AHC Pump.
Indeed I had reverted back to trying the 12volt direct approach again a few days back.

As you all have experienced time and time again, each time you try this or try that the vehicle invariably proceeds to display unexpected behaviours and “off the beaten track expected or anticipated results” which lead us to taking sometimes unexpected options due to some small happening within the system.

Two nights ago the AHC motor displayed somewhat unexpected behaviour in that in direct 12v mode it was pumping fluid straight through to the barrel accumulator and pumping the fluid straight out the bleed screw.

It continued to do this quite aggressively but despite going around the five bleed points at least five times, I could not get the cruiser to show any semblance of rising even slightly.

However, upon entering into another round of bleeding, I noticed the pump changing tone, to the extent I was genuinely worried I had destroyed the pump.
It became less and less aggressive and much much quieter.

Later that night upon reflection I got it into my head that perhaps the pump had actually got clogged or blocked up.

This focused my train of thought upon whether or not to take the AHC pump assembly apart to seek for sludge or any blockage.

The following morning I did just that,

It was surprisingly easier to get to the dissembled stage than I had anticipated, but alas I did make a few mistakes, the biggest one was not taking photographs of each stage and not carefully marking each component to ensure they were replaced precisely and exactly from where they had been removed.

In particular as IndroCruise highlighted the gear wheels would of most certainly been much better if the gears were dissembled in order to be replaced with the exact same gears meshing with each other, tooth by tooth.

However, I had to keep on moving despite these anomalies.

To my great pleasure I found quite a considerable volume of sludge inside the the pump housing End Cap. It is The End cap with the “Cross or plus sign on it”.

To my utter surprise and to be honest, delight I found there was approximately half of an egg cup full of sludge inside this End Cap. (The Temperature sensor is attached to This End Cap.

I used rubber gloves throughout this whole disassemble and reassemble. I continuously jetted the rubber gloves with the aerosol carbon cleaner to ensure the gloves were kept spotless.

I cleaned all components thoroughly before progressing on to disassembling the actual primary pump mechanism itself, the small module that holds the two gear wheels. I will call this assembly The Primary Pump Assembly.

Each and every part was washed and cleaned thoroughly.
Please forgive my crude methods but I found that using a spray can of aerosol carbon cleaner to spray and clean each component to a pristine shine.

I then embarked upon getting the two small filters removed. This was quite a job but boy was I glad I persevered.

May I at this stage once again thank Indrocruise for providing an extensive library of photographs and his detailed description of the pump being taken apart stage by stage.

May I also apologise for not taking photographs as I went through this process. I note how you professional contributors make great use of both photographs and video.
I will endeavour to progress to the use of photographs soon.

However These pictures supplied by Indrocruise are of immense help to anyone contemplating taking on this job.

These pictures are also extremely useful in understanding the following observations and suggestions as regards to rebuilding the AHC pump.

Now back to the Pump filters;

I tried quite a few methods to withdraw them from the housing, initially without success, in the end however I found that using as perfect a fit of wood screw was a perfect solution.
I ground off the point of the screw to prevent it from damaging the very small and very fine mesh of the filter.

I screwed the screw in very tentatively making sure not to go too far and when the screw had sufficient grip I extracted the screw and filter by mocking up a direct lift cantilever type affair that lifted the screw in a directly straight upwards trojectory. Once I got the “tensions” all as near as I could gauge this actually worked very well.

Now I have read in a few posts that some folk have suggested that due to the difficulty of extraction of these very petite and fragile filters, that they opted to not take them out but alternatively they jetted hydrocarbon cleaning fluid both directions from the inlet and outlet orifices.

I fully understand this decision, but upon my findings I don’t agree with trying to clean this way.

This was because I found it was very difficult to clean the small meshes in these petite filters when I had them totally removed from there enclosures never mind attempting to do so by simply blowing from either end of the enclosure.

I found that the debris which was a very fine sand like material was almost embedded like concrete inside the small mesh and to make it even more difficult these small meshes have small overlaps of mesh that must be gently manipulated by squeezing between your fingers to open up these small overlaps or flaps to ensure that all that dust like grain is removed.

It took me about 10 minutes to clean each of these filters thoroughly.
The degree of cleaning needed could not be achieved if the filters are not removed out of there receptacles or enclosures.

One of the filters was much more congested than the other.

I then took a very fine grade nail file and tidied up the top of the brass collar of the small mesh filter to ensure any scrapes or abrasions caused by my extraction were filed down smooth in readiness for reinsertion back into the respective orifices in the respective pump body parts.

When the pump body components are all thoroughly thoroughly cleaned ensuring that all the internal channels and journals are cleansed with certainty that the unseen portals or journals or oil-ways are absolutely spotlessly cleansed, then and only then the small filters must be reinserted.
I found it was necessary to press these small filters back into place.
I used vice grips with small pieces of rubber to protect the components from any damage.

This next stage is very very important,

The gear wheels and gear “axle” are a single unit with the gear wheel and the axle being milled as a single piece.

These axles fit into two small hubs that in turn press freely into the pump housing.

Here I made what could be a very significant observation,

There is a very petite cut-away or “Nick” machined out of the bottom edge of one of these hubs.

It is vital that these hubs are replaced hub by hub, back into the housing precisely back into the position they came out of.

Thankfully there are only two options or ways to instal these hubs into the housing.

For ease of explaining from here, let’s just say there is the right way and there is the wrong way.

However, installing the right way the fluid can flow unimpeded on its proper pathway,
However installing the wrong way, the pump cannot function as the aforementioned “nick” is in the wrong place thus the fluid cannot flow unimpeded.

I know I may be wrong here but so far I have never heard anyone mention this small “Nick” and boy is it not a vital part of the pumps mechanism. I have read and studies hundreds of posts as well as watched many videos but to date I have never heard of or been told to look out for this petite “Nick”.

Now as I admitted earlier I didn’t take notes or photograph indeed I took no actual records of the disassemble as I should have done.

Boy did I have a problem here,
“How do I know which way to re-instal these hubs”

In the end I did a miniature mock up of the assembly and using a fine nozzle and compressed air, I blew the air into the inlet hole on the housing, and indeed yes my first attempt was wrong as the air was not getting through. So now I knew to insert the hubs the alternative way.

So by the skin of my teeth I got past this hurdle.

I however could not get out of the next slip up so easily.

I hadn’t marked and recorded exactly where the teeth of the gear wheels met, tooth by tooth.
In this my friends I was defeated.
I had to proceed and hope that the pump would function for me with just a random guess with positioning the two gear wheels.

I wish to share another idea here if I may.

When I was assembling the components of the primary pump assembly I set up a very clean plastic jar in which I filled with AHC fluid.

I then set the components of the primary assembly into the AHC fluid and I assembled each component under the fluid ensuring each orifice was filled with AHC fluid from the onset of assembly.

This method also meant that all the components of the primary pump were assembled while submerged in the AHC fluid thereby ensuring that all the components were adequately lubricated as the assembly progressed.

Next step is to attach the Main Block of the pump to the primary pump module.
Being conscious of the need to avoid any and all air pockets I unscrewed the AHC Fluid pressure sensor out of the main block, filled the pressure switch orifice with AHC Fluid and then reinstated the AHC fluid pressure sensor back into the main block. I then set the “main block” on its side with the large End Cap O Ring looking straight upwards and the electric motor directly beneath sitting on the bench.

There is a second much smaller O Ring sitting inside the large O Ring, on this block face. It is vital this small o ring is kept in its place.

It is crucial to make sure it is kept in place. I believe this O Ring seals the faces of the two assemblies at the orifice that allows fluid access to the pressure sensor.

I filled AHC fluid into the upper face of this main block before dropping the primary pump assembly down into the block. Once again attempting to ensure that all orifices were filled with fluid and all joints lubricated.

There are a two other O RIngs who’s locations are obvious. However these two small O Rings have two small steel backing washers.
It is vital to replace these washers and O Rings precisely in the order they come of. However thankfully this is also intuitive in nature and can be worked out.
The washer and O Ring sit into a recess.
The washer goes into the orifice first, then the O Ring.

One other observation I made was that if you happen to slightly over tighten the primary pump assembly to the “main block” the pump will be too tight and the motor won’t be able to turn the gears in the gear Housing.

There are proper torque settings for tightening these four studs, but I couldn’t find them at the time.

So I just trusted in my experience and I lightly tightened each stud while at the same time I tested the motor by connecting to a 12volt battery, thereby being able to identify when I was coming closer to the “Sweet Spot”

Now the final “trick” I have to offer is as follows.

The final step of this stage is to attach The End Cap or housing, the black cap with three stud holes in which the primary pump assembly is housed. Or the black cap with the pressed “+” sign and with the temperature sensor attached.

Once again in an effort to ensure all orifices are filled with AHC Fluid, I got a large plastic dish.
The plastic dish was of a size that I could set the the End Cap upside down with the three protruding stud hole tags sitting on the edge of the plastic container.

I then filled the End Cap with AHC fluid.

Next I set the whole pump assembly down onto the end cap submerging the primary pump assembly into the AHC fluid once again in an effort to minimise any and all air pockets as the pump is assembled. The overflow of AHC fluid dropped cleanly into the plastic dish below thus saving it cleanly.

It is very important to make sure this dish is kept very clean so as to be able to reuse the overflowing AHC fluid.

I carefully inserted and tightened the three studs thereby sealing the End Cap onto the whole pump body.

All of the above “exercises” were conducted in an effort to ensure all the internal cavities of the pump were filled with clean AHC fluid and that all moving parts were adequately lubricated throughout the assembly.

And Finally,

I uncoupled the cruisers negative battery earths and didn’t refit for periods 20 minutes.

This was to attempt to rest the AHC ECU.

I then refitted the AHC FLUID reservoir on top of the pump. However I filled the reservoir receptor orifice with AHC fluid once again to attempt avoid any air pockets.
I then re installed the reservoir onto the pump.

I put some oil into the reservoir.

I re-installed the AHC pump assembly back into the cruiser. I re-joined the three plugs, the 12volt motor supply, the temperature sensor and the pressure sensor and the main AHC Fluid “out” line.

Then I half filled the reservoir with AHC Fluid.

I bled the outlet pipe again using the 12volt direct method, and then retightened the output pipe.

I then reconnected my battery negative terminals.

I wasn’t sure if I would need to use “The Active Test “ to get the pump going, indeed I still wasn’t sure if the pump would work.

To my great pleasure I noticed the AHC FLUID exiting the reservoir at quite a speed, and eventually after perhaps 2 or 3 ignition off / on and start engine again cycles.

And magically for the first time in over 3 months the front of the cruised began to rise. I had to keep cycling the ignition from on / off and restart a number of times and was delighted to See the rear of the vehicle rising.

I must admit I was very surprised that the cruiser lifted right up to its maximum height without any further bleeding.

I know i must bleed all the 5 points a few times tomorrow but
As it was now quite late here I decided to take the cruiser for a drive and I was of to bed.

It was absolutely wonderful being able to drive on bumpy and pot-holed roads without having to slow down to avoid the bumps and bangs, as I had to do for the past 3 months.

I realise I must bleed the system systematically tomorrow and hopefully I will get the front and rear heights sorted as well tomorrow.

One thing I noticed was that the cruiser was very fast in lifting from L to N and then from N to H.
I didn’t think of timing the rise but I believe it would be from Low to N in less than 10-15 seconds and the same from N to H.
However I don’t think it took anything near 30 seconds to get from L to H.

There are a few issues still needing sorted.

Although the cruiser lifted up to H, the green light AHC display only went up to N.
But when lowering, I press the down button once and the cruiser dropped a stage and the green light went down to L. However when I pressed the Down button again the cruiser drops down to the lower position.

I suspect two issues may be at play here,

1,
The rear height sensor is not adjusted correctly. I do remember moving it to a different position a few weeks back when I took the height sensors off the cruiser for testing.

2,
Given that I have installed new rear struts and new springs, it is highly possible the Torsion Bars will need adjusting.

But first I must bleed the system properly.

I can’t believe the cruiser actually managed to go from a complete pump rebuild to raising the cruiser to H without using Active Mode or without the AHC OFF light ever coming on.
I am also very pleased at how fast the cruiser raised up.

I cannot stress enough how difficult it was to clean the dust grit from between the flaps of the internal mesh filters mentioned above

In my opinion that grime in those flaps will cause a very high % loss of available through flow potential of AHC fluid going in or out of the AHC pump. The worst affected filter was the in-flow filter from the End Cap into the pump. Judging by the actual physical petite size I believe one could lose upwards on 80% of available fluid throughout.

I have no idea if my theory of reassembling the AHC pump while submerged in clean AHC fluid has had any specific benefit but I do know I am more than impressed how fast and efficiently this 24 year old pump has worked in the initial reinstating of the cruisers AHC from a complete cleanse and rebuild to what could be described as being in a “good” operational stare.

Albeit the system needs further refining and tidying up as mentioned above.

I know this is a long post, but I am writing it in the hope that someone will perhaps avoid certain mistakes and more importantly hopefully avoid the long lag time it took me to eventually find out what was wrong with my AHC system.

Thank you to all who contributed and a big thank you to Indrocruise for the meticulous directions and guidance which was presented in a totally non judgmental manner. I totally acknowledge I am a novice and I made quite a few mistakes as we went through this AHC recovery.

Now for a bit of shut eye, I hope.

May I please bring your attention to Indrocruise post #943.
There are some fantastic photographs in this post by IndroCruise. We owe much gratitude for this content and all the others who make such like contributions on the Forum.
It is a privilege to be a member of a forum of such calibre.

If you look closely at the very first photograph, you can see the small Nick cut out of the bottom edge of only one of the two hubs or barrel like components.
If this “Nick” is not repositioned back in its original place this restricts the flow of fluid through the pump.

IndroCruise has presented a brilliant collection of close-up photographs in this post, including the small filters showing the overlaps or flaps that I had difficulty cleaning the compressed grime out of.

It’s actually astounding that all the volume of oil required to lift and lower your vehicle has to flow through these petite filters.

Hope this helps next “on need of help” forum member.

 

[wsudu]

I was flushing and exchanging fluid last night and all was going well, until the driver rear bleeder which was rusted and would not bleed so I had to take it all of the way out. So dumb question, I'm assuming this introduced air into to the system which I need to bleed out again. Do I start in the same order (Front L, Accumulator, Rear L, Rear R, Front R) and do I even need to bleed the accumulator? Or should I be doing something different?

 

[2001LC]

I was flushing and exchanging fluid last night and all was going well, until the driver rear bleeder which was rusted and would not bleed so I had to take it all of the way out. So dumb question, I'm assuming this introduced air into to the system which I need to bleed out again. Do I start in the same order (Front L, Accumulator, Rear L, Rear R, Front R) and do I even need to bleed the accumulator? Or should I be doing something different?

You may not have introduced air, provide you did not jack up the vehicle while bleeder open. As you would have been on the bump stops. But you can just bleed off a little from that bleeder to see. Naturally you'll need to start engine once reservoir filled, to build pressure again with all bleeders torqued in. Then bleed just a little. You can start bleed from L, N or H. But L, never raising to N or H is best in this case.

 

[Urtwob]

Late edit: Pictures added at end of message

Well, it seems like you have made a discovery!! No need or point in beating up on yourself -- we all learned about the AHC system by doing, with 'hands-on', and with plenty of 'educational' mistakes along the way! Press on!

The AHC system looks after itself quite well -- some would say too well, because diagnosis sometimes can be quite baffling! The positive is that if your AHC Pump has run low on fluid, the Pump will simply stop -- due to one or more of the so-called 'fail-safe functions', in this case initiated by the Pressure Sensor sensing low internal pressure and the ECU causing the Pump to stop very quickly -- see details at page DI-229 (for C1718), page DI-252 (for C1751) and most importantly page DI-257 (for C1762) in the "Diagnostic" extract from the FSM, provided at Post #952 in this thread.

The Pump will not run when it is dry. At this point the AHC actions are prohibited by the system. The AHC system is no longer active.

The "Active Test" is the FSM-prescribed procedure to restart (actually prime) a stopped Pump, and allow the AHC system to be re-pressurised.

The fact that the "Active Test" does not work on your vehicle is indicative of several possible problems -- of which AHC Pump blockage is one possibility, foreshadowed as “Alternative #2” back at Post #908 in this thread and in related posts by @2001LC.

May I say that the accumulation of debris in the housing around the AHC Pump is not surprising in a 24 years old vehicle. This is one of the known accumulation places – the other common accumulation places are in the ‘shock absorbers’. Materials which lodge in these places can be difficult to shift, because AHC Fluid does not really circulate but just goes backwards and forwards when the system is operating.

The best approach to ‘hydraulic hygiene’ is to change out the AHC Fluid frequently – evacuate the AHC tank and discard the fluid, replace with new AHC Fluid, then carry out long bleeds with new AHC Fluid at all five (5) bleeding points until new, clean bubble-free fluid is observed. This will not be perfect because a straight-through complete flush is not possible on the AHC system and some residue will remain – which is even more reason to do this frequently.

At the same time, it is wise to replace all five (5) bleeder valves and all (5) protective caps on the bleeder valves. The cost of replacement is tiny. The cost and inconvenience of dealing with old bleeders frozen with rust is HUGE.

In my personal opinion, the fluid changeout should be done at least every three (3) years. My recollection is that the Owner’s Manual recommends every six (6) years or every 60,000 miles (100,000 kilometres) – too far apart for me!

The fluid used must be only genuine Toyota/Lexus AHC Fluid, such as international Toyota/Lexus Part Number 08886-01805, supplied in 2.5 litre steel drums and manufactured by Japanese oil company Idemitsu Kosan Co., Ltd, or, it may come in different packaging with a different Part Number in some markets. Use of other fluids, such as brake fluid, auto transmission fluid, steering fluid, invites complete disaster by degrading seals and membranes, thereby reducing the life of ‘globes’ and seals and increasing debris and increasing blockage risks in the AHC system.

Recently, you have replaced ‘globes’ and ‘shock absorbers’. This would have involved bleeding of a lot of fluid, so unless incorrect fluid was used or old dirty fluid was recycled, the AHC Fluid in your system should be quite good – but obviously it has not ‘flushed out’ the accumulation you have discovered.

Following below are some informative links to background information and pictures of Pump internals, including the only diagram of the AHC Pump internals to be found in the Factory Service Manual (FSM), together with information about the screens/strainers within the AHC Pump ....

Previously, @PADDO made observations at Posts #16 and #19 in the thread below:

AHC help needed

I hooked my 2002 LX470 with 80K miles up to techstream yesterday to see what my neutral pressure readings were after replacing my globes. I was only getting like 6 graduations from the old globes and my front suspension felt like it was stuck in sport mode. After replacing the globes I have...

forum.ih8mud.com

At this post #19 in the above link, it is noted that:

“The two screens are internal to the pump so the pump/reservoir assembly needs to be removed from the vehicle. It’s then a matter of taking off the circular external pump housing which gives access to the pump. It’s retained to the main body and held together, its a sandwich design, by four cap screws. Undo the screws, and disassemble the pump sandwich and the screens are revealed. They are pressed in and can be cleaned in situ with a blast of 100% hydrocarbon cleaner or you can back them out with a pick to clean. Reassemble, install the pump/reservoir fill with fluid and let it sit for a while to assist the fluid in working it’s way into the pump housing/intake and fire it up. If it times out because it’s airlocked and can’t prime then force run it manually**”.

* in other words, something that dissolves oils and evaporates readily without leaving a residue, so not a detergent.

** means operation of the pump by “Active Test” for about 10 seconds with AHC fluid at correct level or better in the tank, or operation by direct connection of the pump motor to the battery.

My further notes: If a clean-up is being done, it is worth disassembly of the pump to investigate the screens/strainers which are are located inside the actual pump itself, on the input and output sides of the tiny gears (smaller than a thumbnail) which provide the actual pumping action. Gear pumps usually are specified for high pressure / low volume applications where the fluid is free of particulates. The screens/strainers are intended to keep particulates out of the actual pump. Particulates might otherwise degrade or destroy the gear action.

When an AHC Pump is thought to have failed or a relevant DTC such as C1762 is recorded – meaning that the delivered pressure is too high or too low and AHC response is slow – this may have been caused by clogged screens/strainers rather than problems in the actual pump, unless the screens are missing or have holes which allow particles to pass into the gears. The pump is small but fit for purpose -- it would take something like a stream of sand to destroy the pump.

Many pictures of the Pump internals including the screens/strainers are found in Post #67 through to Post #70 in this next link and include my pictures of disassembly of my AHC Pump:

AHC pump out? With code 1762

I have seen 1.x was able to program key, customize telescoping, door lock, window and sunroof settings. The 1.x cable I own was able to program my key, disable my DRLs, and stop that annoying auto-telescope wheel from activating. I have a 01LX that doesn't have TPMS, and I have read multiple...

forum.ih8mud.com

The problematic internal strainers/screens (not to be confused with the strainer at the AHC Tank) are shown at Post #70 in the above thread.

The main purpose of the pump cover with the big "+" on the outside is to contain the pressure which is used to force the pump gears tightly onto the pump body so as to minimise side clearances and minimise fluid bypassing the gears at their sides. There won't be much flow in the space inside this cover but outside the actual pump. It is a natural trap for fluid.

As for many types of oils warmed and cooled over a long period of time in the presence of oxygen and moisture, a gel or sludge eventually will form in traps where fluid is stationary or moves slowly. Some of this gel or sludge may find its way into the pump. If so, it will be caught at the internal screens/strainers inside the pump along with any accumulation of particulates not fine enough to pass through the screens/strainers. The pressure drop across the wholly or partially blocked screens/strainers will cause a loss of pump output pressure and flow.

So a clean-out is a good idea when there are suspicions about pump delivered pressure and flow being low and/or DTC C1762.

A source of replacement internal screens/strainers is not known -- they are not detailed in the FSM and do not appear on commonly available parts diagrams and lists and are not shown on Toyota/Lexus lists. It is not known which of the many suppliers to Toyota/Lexus factories is the actual manufacturer of the AHC Pump. It is suspected that it might be KYB who make the Height Control Accumulator used on LC100/LX470. The FSM deals with the issue only by recommending replacement of the AHC Pump rather than repair.

The screens/strainers could be eased out with a pick as mentioned by @PADDO -- but carefully, do not want any holes in the mesh. A simple backwash may be a safer approach.

Alternatively, and for peace of mind, replacing the pump sub-unit every 15 to 20 years (or 24 years!) may not be such a bad idea – especially where long term neglect (infrequent AHC fluid changes and infrequent AHC pressure checks) by previous owners is suspected. The pump sub-unit is Part Number 48901-60010 – current price example: Partsouq: USD168.19 plus delivery.

Suggest if disassembling the pump to clean the internal screens/strainers, then either leave the tiny gears and their carriers in place, or, carefully mark and photograph their orientation to one another so that all parts can go back together with parts and gears oriented and meshing in exactly the same way. Otherwise, the Pump may not work at all. Ideally, replace all o-rings encountered and also the oil seal between the pump and the motor and the grommet between the AHC Tank and the AHC Pump.

Suggest if using a secondhand pump, disassemble and clean the screens/strainers and inspect the gears before installing in the vehicle.

Also suggest bench testing the overall Pump/Motor assembly with a direct 12 volt supply before reinstalling it in the vehicle.

For better peace of mind, suggest consider replacing the AHC Pump with a new Pump (not the whole assembly of Pump, Sensors, Motor, Tank -- just the Pump). The motor driving the pump is a very long-life unit -- you may wish to disassemble to inspect the bearings and brushes etc, although it is worth being aware that there are few if any reports on IH8MUD of failure of this motor.

Suggested purchases:

48901-60010 – AHC Pump,
90301-70003 – large O-ring for AHC Pump,
90301-06012 – small O-ring for AHC Pump,
47255-60010 – grommet between AHC Tank and AHC Pump,
49189-60010 – replacement bleeder valves (5 required),
49177-60010 – replacement bleeder caps (5 required),
08886-01805 – AHC Fluid in 2.5 litre steel drums, at least two, probably three drums,

Probably, around USD200 in total for new OEM units in the above list, delivered from the overseas suppliers, such as Toyota | Parts Catalogs | PartSouq - https://partsouq.com/en/catalog/genuine/locate?c=Toyota. Partsouq is used by many IH8MUD Members including me, unless local Toyota/Lexus dealers can come close to the prices found on the Partsouq catalogue + delivery etc. Prices in various currencies and delivery costs to different locations around the world can be found on this website without obligation to buy.

Some visuals of actual disassembly of an AHC Pump internals, gears, etc, can be seen on Youtube. These often are not LC100/LX470 AHC Pump assemblies but instead are LC200 Pump assemblies -- these are distinguishable by the Attenuator (small brown cylindrical object) mounted next to the actual AHC Pump. The Attenuator is located separately below the AHC Pump on LC100/LX470. The LC200 AHC system is quite different -- and the tank, pump, motor etc are mounted in the RHS rear quarter panel behind the RHS rear wheel. The actual Pump internals on LC200 appear much the same (and may be exactly the same) as the LC100/LX470 Pump and the visuals give the idea. However, it is safest to rely on the pictures on the various IH8MUD "100 series" threads.

I don't mean to be pessimistic but it does appear that there may be multiple faults on your AHC system. The good news is that all parts of the AHC system definitely are repairable -- and at reasonable costs. One thing at a time -- today it is the AHC Pump!

Further down the track when the AHC system is working again and ready for adjustment, the video on Youtube prepared by @suprarx7nut a.k.a. AHC Info - https://www.yotamd.com/blogs/news/ahc-info is the "go to" video. By then, Techstream will be essential.




LC100/LX470 Pump disassembled (picture by @IndroCruise )
View attachment 2974119


Strainer position -- enlarge to see insider strainer below brass ring (picture by @IndroCruise
View attachment 2974121


Strainer position -- enlarge to see insider strainer below brass ring (picture by @IndroCruise )
View attachment 2974122


Strainers removed and cleaned (picture by @Zel)
View attachment 2974123


Overall layout of LC100/LX470 Assembly of Pump, Motor, Pressure Sensor, Temperature Sensor, Tank:
View attachment 2974129

Hi #indrocruise

This is a another project altogether.
Once again there is an element of trying to help someone out with this project.

I am not a LC 200 owner yet.
However I have been asked to look at an AHC problem on a Cruiser belonging to a friend.
This Cruiser has been modified to suits its owners disability needs. The Lady owner is in real need of getting the Cruiser back on the road as she is basically isolated at home without it.

The simple history.

This is a 2007 LC200
It suffered a burst front hydraulic shock and I believe it was driven for a few days down on the bump stops.

A new shock was installed however no one has been able to get the system going again.
A very talented young auto electrician has had a go and another mechanic.
They have had no joy.

As you are aware I have just recently had a significant AHC journey with my LC 100 and eventually after a lot of collaborate research with your kind self and others on the forum Ithe problem was solved by taking the AHC pump off, totally disassembling, thoroughly cleansing including the two small micro filters.
So after this 3-4 week journey leading to focus on the AHC PUMP, when I reinstalled the pump my AHC problem was solved.

So I took the AHC pump out of the LC200 yesterday. Did a thorough cleanse.
I rebuilt it, checked it was running and more importantly made sure it was pumping fluid.

Howeve sadly this has not solved this cruisers problem.

One thing I see is that the AHC OFF Light is constantly blinking from the instant you turn on the ignition.

I have carried out a AHC RESET but this has not worked.

Question my friend,
(Are all the test procedures and rest procedure, the same on both the LC100 and LC200?)

However when I have crossed poles Tc and E1 and pressed the brake pedal 9 times within 3 seconds, the AHC OFF Light did change its blinking sequence.

It went from a regular 1 second On Off On Off continuous to an ON OFF ON OFF pause ON OFF ON OFF ON OFF pause continuous repetitive pattern. Ie 2 x ON THEN 3 x ON repetitive pattern.

But when you finalise the reset process removed the link and press the OFF button for up to 10 seconds and go back to a normal start up, it instantly goes back to a continuous flashing On Off pattern even when you start the cruiser.

I would truly appreciate any and all advice or guidance on this please.
I have checked all AHC fuses and the AHC Relay under the hood.

That said I am not sure yet about the fuses inside the passenger side inside kick panel.
Are they the same layout as the LC100 fuses in there?

The AHC ECU was tested as well by the other auto electrician before I received the cruiser. He could not find any fault in the ECU. That said, I have no option but to still regard the AHC ECU as being open to investigation again.

I DID run the hydraulic pump manually and the new oil level in the tank / reservoir dropped by about an inch but I could not see the cruiser rise either front or back.
However it prove to me that the pump was moving AHC oil out to the system somewhere.
I suspect it probably just filled the main barrel height control actuator but not any of the globes or the hydraulic rams / shocks as solenoids are probably closing off these routes.

Any help or guidance will be much appreciated #Indrocruise.

To finish, may I ask
What does the continuous repetitive ON OFF AHC light blinking normally mean?

Thank you.

Thank you.
URTWOB.

 

[2001LC]

It may be and easy fix, if your lucky.

If the 2007 200 series land cruisers, is like the USA 200 series AHC. Which AHC is only in Lexus LX570 that came out 2008. Where the pump is behind RR wheel well. Those 200 series system shuts themselves down. If we remove fluid from 1 globe and the accumulator at the same time. If some how this happens to her 07 200 series, this could be your issue.

If you've Tech stream cable, try going into active test and or utility. Run system from within tech stream. I don't recall which active test or utility, as been a few years since I've done this.

You mentioned you ran pump. I assume by jumping with 12 volts at motor. If don't have tech stream, try running pump longer, until vehicle raises.

 

[IndroCruise]

Hi #indrocruise

This is a another project altogether.
Once again there is an element of trying to help someone out with this project.

I am not a LC 200 owner yet.
However I have been asked to look at an AHC problem on a Cruiser belonging to a friend.
This Cruiser has been modified to suits its owners disability needs. The Lady owner is in real need of getting the Cruiser back on the road as she is basically isolated at home without it.

The simple history.

This is a 2007 LC200
It suffered a burst front hydraulic shock and I believe it was driven for a few days down on the bump stops.

A new shock was installed however no one has been able to get the system going again.
A very talented young auto electrician has had a go and another mechanic.
They have had no joy.

As you are aware I have just recently had a significant AHC journey with my LC 100 and eventually after a lot of collaborate research with your kind self and others on the forum Ithe problem was solved by taking the AHC pump off, totally disassembling, thoroughly cleansing including the two small micro filters.
So after this 3-4 week journey leading to focus on the AHC PUMP, when I reinstalled the pump my AHC problem was solved.

So I took the AHC pump out of the LC200 yesterday. Did a thorough cleanse.
I rebuilt it, checked it was running and more importantly made sure it was pumping fluid.

Howeve sadly this has not solved this cruisers problem.

One thing I see is that the AHC OFF Light is constantly blinking from the instant you turn on the ignition.

I have carried out a AHC RESET but this has not worked.

Question my friend,
(Are all the test procedures and rest procedure, the same on both the LC100 and LC200?)

However when I have crossed poles Tc and E1 and pressed the brake pedal 9 times within 3 seconds, the AHC OFF Light did change its blinking sequence.

It went from a regular 1 second On Off On Off continuous to an ON OFF ON OFF pause ON OFF ON OFF ON OFF pause continuous repetitive pattern. Ie 2 x ON THEN 3 x ON repetitive pattern.

But when you finalise the reset process removed the link and press the OFF button for up to 10 seconds and go back to a normal start up, it instantly goes back to a continuous flashing On Off pattern even when you start the cruiser.

I would truly appreciate any and all advice or guidance on this please.
I have checked all AHC fuses and the AHC Relay under the hood.

That said I am not sure yet about the fuses inside the passenger side inside kick panel.
Are they the same layout as the LC100 fuses in there?

The AHC ECU was tested as well by the other auto electrician before I received the cruiser. He could not find any fault in the ECU. That said, I have no option but to still regard the AHC ECU as being open to investigation again.

I DID run the hydraulic pump manually and the new oil level in the tank / reservoir dropped by about an inch but I could not see the cruiser rise either front or back.
However it prove to me that the pump was moving AHC oil out to the system somewhere.
I suspect it probably just filled the main barrel height control actuator but not any of the globes or the hydraulic rams / shocks as solenoids are probably closing off these routes.

Any help or guidance will be much appreciated #Indrocruise.

To finish, may I ask
What does the continuous repetitive ON OFF AHC light blinking normally mean?

Thank you.

Thank you.
URTWOB.

The AHC/AVS systems on a Toyota Land Cruiser LC200 (where fitted) will be much the same (I suspect exactly the same) as the AHC/AVS systems fitted to all Lexus LX570 vehicles.

However, while some of the basic principles are similar, the systems on these “200 series” vehicles have evolved a long way from the more basic AHC/TEMS systems fitted to the Land Cruiser LC100 (where fitted) and the Lexus LX470. The more modern system is considerably more complex in its designed functions and in its operation.

The monitoring and specific testing arrangements are different between the earlier and the later suspension systems.

In the Australian market, the more advanced AHC/AVS systems were reserved exclusively to the 5.7 litre V8 gasoline (petrol) Lexus LX570 (and to a 4.5 litre V8 turbodiesel variant labelled here as the Lexus LX450d). As always, Toyota and Lexus segment their markets differently in various different parts of the world and there are differences between models and features in the different markets.

Some the differences can be gleaned from the two attachments between the earlier AHC/TEMS system (1998 to approx 2007) and the later AHC/AVS system (approx 2007 to 2022) by reading and comparing the two attachments

While I do have an October 2020 4.5 litre V8 turbodiesel (then) top-of-line Toyota Land Cruiser LC200 (designated ‘Sahara’ in the Australian market), the AHC/AVS systems are not fitted to this model. Instead it has the Kinetic Dynamic Suspension System (KDSS) which is completely different, less sophisticated and serves a different purpose to both the “100 series” AHC/TEMS systems and the “200 series” AHC/AVS systems.

I have occasionally driven a Lexus LX570 and I did contemplate purchase of an LX450d, but I have not researched nor worked on their AHC/AVS systems.

May I suggest that the following link to a thread in the IH8MUD “200 series” Forum may provide a useful starting point for learning about the AHC/AVS systems on “200 series” vehicles:

LX570 AHC “Basics” - Added as sticky thread for AHC Issues - https://forum.ih8mud.com/threads/lx570-ahc-basics-added-as-sticky-thread-for-ahc-issues.1053154/

Suggest that a search of “bleed” or “bleeding” in this thread would be a productive start and may give some insights. As @2001LC already has mentioned, bleeding may only be a matter of perseverance. The relevant "200 series" FSM sections on AHC/AVS may be helpful if a link can be found to them.

Even though the systems are different, my understanding is that ”the continuous repetitive ON OFF AHC light blinking normally means” that the AHC/AVS system is “OFF” (not operating).

My instincts would be that there are many other possible causes of the system being “OFF” (not operating) – such as the causes of the various possible ‘fail safe functions’ on the “200 series” AHC/AVS system. These need to be eliminated before arriving at the less likely conclusion that there is a problem with the ECU.

I do suggest that it is close to impossible to do long-distance diagnosis of AHC/AVS issues on “200 series” vehicles without the help of both Techstream and input from persons (such as from IH8MUD) who know their way around this system. There will be some Diagnostic Trouble Codes (DTC’s) in the circumstances described and it would be very helpful to know which ones are appearing.

 

[Urtwob]

The AHC/AVS systems on a Toyota Land Cruiser LC200 (where fitted) will be much the same (I suspect exactly the same) as the AHC/AVS systems fitted to all Lexus LX570 vehicles.

However, while some of the basic principles are similar, the systems on these “200 series” vehicles have evolved a long way from the more basic AHC/TEMS systems fitted to the Land Cruiser LC100 (where fitted) and the Lexus LX470. The more modern system is considerably more complex in its designed functions and in its operation.

The monitoring and specific testing arrangements are different between the earlier and the later suspension systems.

In the Australian market, the more advanced AHC/AVS systems were reserved exclusively to the 5.7 litre V8 gasoline (petrol) Lexus LX570 (and to a 4.5 litre V8 turbodiesel variant labelled here as the Lexus LX450d). As always, Toyota and Lexus segment their markets differently in various different parts of the world and there are differences between models and features in the different markets.

Some the differences can be gleaned from the two attachments between the earlier AHC/TEMS system (1998 to approx 2007) and the later AHC/AVS system (approx 2007 to 2022) by reading and comparing the two attachments

While I do have an October 2020 4.5 litre V8 turbodiesel (then) top-of-line Toyota Land Cruiser LC200 (designated ‘Sahara’ in the Australian market), the AHC/AVS systems are not fitted to this model. Instead it has the Kinetic Dynamic Suspension System (KDSS) which is completely different, less sophisticated and serves a different purpose to both the “100 series” AHC/TEMS systems and the “200 series” AHC/AVS systems.

I have occasionally driven a Lexus LX570 and I did contemplated purchase of an LX450d, but I have not researched nor worked on their AHC/AVS systems.

May I suggest that the following link to a thread in the IH8MUD “200 series” Forum may provide a useful starting point for learning about the AHC/AVS systems on “200 series” vehicles:

LX570 AHC “Basics” - Added as sticky thread for AHC Issues - https://forum.ih8mud.com/threads/lx570-ahc-basics-added-as-sticky-thread-for-ahc-issues.1053154/

Suggest that a search of “bleed” or “bleeding” in this thread would be a productive start and may give some insights. As @2001LC already has mentioned, bleeding may only be a matter of perseverance. The relevant "200 series" FSM sections on AHC/AVS may be helpful if a link can be found to them.

Even though the systems are different, my understanding is that ”the continuous repetitive ON OFF AHC light blinking normally means” that the AHC/AVS system is “OFF” (not operating).

My instincts would be that there are many other possible causes of the system being “OFF” (not operating) – such as the causes of the various possible ‘fail safe functions’ on the “200 series” AHC/AVS system. These need to be eliminated before arriving at the less likely conclusion that there is a problem with the ECU.

I do suggest that it is close to impossible to do long-distance diagnosis of AHC/AVS issues on “200 series” vehicles without the help of both Techstream and input from persons (such as from IH8MUD) who know their way around this system. There will be some Diagnostic Trouble Codes (DTC’s) in the circumstances described and it would be very helpful to know which ones are appearing.

Thank you for such a comprehensive and prompt reply #Indrocruise.

May I ask, is it possible the LC200 could be OND11 or is it still likely to be MOBD?

I ask as I have Techstream and the appropriate scanner cable for OBD11
But sadly not for MOBD

I must get the elm set-up that you have indicated before.

 

[IndroCruise]

Thank you for such a comprehensive and prompt reply #Indrocruise.

May I ask, is it possible the LC200 could be OND11 or is it still likely to be MOBD?

I ask as I have Techstream and the appropriate scanner cable for OBD11
But sadly not for MOBD

I must get the elm set-up that you have indicated before.

Actually, as well as gasoline (petrol) engines, Techstream should work on the Toyota-specific MOBD system such as on 1HD-FTE and other Toyota diesels – but I experienced many frustrations.

I gave up when I found that for AHC purposes I could use a simple and cheap dongle called “ELM327 Mini Interface” – widely available on Amazon and eBay for around USD11.00. This plugs into the DLC3 port under the dashboard.

Then add to that the following App which connects the dongle by Bluetooth to an Android device (preferably a tablet for a bigger screen than a phone):
ELMScan Toyota - Apps on Google Play - https://play.google.com/store/apps/details?id=com.obd2.elmscantoyota (Cost: around USD6.00 if I remember correctly).

While very convenient (especially when travelling, or to have screen next to you without a cable when doing Height Control Sensor adjustments), there is much wider functionality on Techstream, so may I suggest that you also persist with acquiring Techstream and setting that up if you can – just as I will, eventually ….

Laws passed by Governments (and not Toyota) determined when OBD2 became mandatory. This link gives some background but the statements should be checked with the automobile association or other authority in your Country:

On-Board Diagnostics (OBD) Background History - https://www.obdinnovations.com/on-board-diagnostics-obd-background-history/

This source includes the statement:

The EOBD (European On Board Diagnostics) regulations are the European equivalent of OBD-II, and apply to all passenger cars of category M1 (with no more than 8 passenger seats and a Gross Vehicle Weight rating of 2500 kg or less) first registered within EU member states since January 1, 2001 for gasoline engine cars and since January 1, 2004 for diesel engine cars.

For newly introduced models, the regulation dates applied a year earlier - January 1, 2000 for petrol and January 1, 2003 for diesel.

For passenger cars with a Gross Vehicle Weight rating of greater than 2500 kg and for light commercial vehicles, the regulation dates applied from January 1, 2002 for petrol models, and January 1, 2007 for diesel models.

The technical implementation of EOBD is essentially the same as OBD-II, with the same SAE J1962 diagnostic link connector and signal protocols being used.

With Euro V and Euro VI emission standards, EOBD emission thresholds will be lower than previous Euro III and IV.

So whether the vehicle in UK under discussion in this thread is OBD2 or not will depend on whether it is gasoline (petrol) or diesel and the precise date these ‘rules’ were commenced by the UK Government. Seems strange, but remember that the political and legislative driver was environmental concerns at that time about vehicle emissions. If OBD2, then there should be a compliance label to that effect in the engine bay.

 

[Urtwob]

Hi Everyone.
Can anyone help please,
#Indrocruise @IndroCruise.

A 2007-8 LC 100 4.2 diesel. UK/Ireland.
Does anyone know if the AHC ECU and adjoined AHC relay are in below the steering wheel above foot rest, just as it is in the earlier 1998-2003 LC100?

My problem is that this car the 2007-2008 has been modified for a disabled driver and getting in to where I suspect the ECU is located is going to be quite a job.

However I have had a peak with a probe or magic eye and I actually can’t see it where I thought it should be.

Anyone have any knowledge of the Later LC100 layout as regards the position of the AHC ECU and adjoined Relay.

Thank you everyone.
Any help much appreciated.

 

[IndroCruise]

Hi Everyone.
Can anyone help please,
#Indrocruise @IndroCruise.

A 2007-8 LC 100 4.2 diesel. UK/Ireland.
Does anyone know if the AHC ECU and adjoined AHC relay are in below the steering wheel above foot rest, just as it is in the earlier 1998-2003 LC100?

My problem is that this car the 2007-2008 has been modified for a disabled driver and getting in to where I suspect the ECU is located is going to be quite a job.

However I have had a peak with a probe or magic eye and I actually can’t see it where I thought it should be.

Anyone have any knowledge of the Later LC100 layout as regards the position of the AHC ECU and adjoined Relay.

Thank you everyone.
Any help much appreciated.

There is a picture at this link to Post #102 of the position of the Suspension Control ECU and AHC Main Relay in the Driver's footwell in a USA Left Hand Drive vehicle (the AHC Main Relay is missing in this example but the holder can be seen). This may help to visualise the Left Hand Drive situation.

Quick question about AHC ride with extra weight

Hey guys, I have a 2006 land cruiser and I like the ride on it for the most part but I feel I may be missing out on something due to having AHC problems. Everyone says the land cruisers ride like clouds, but its not all THAT smooth to me. It rides pretty good, but only slightly better than my...

forum.ih8mud.com

In your Right Hand Drive vehicle, the Suspension Control ECU and attached AHC Main Relay is in an analagous position on the left leg side of your Driver's footwell -- unless it has been moved during modifications.

Suggest probe above and slightly to the left of the DLC3 socket.

Also suggest go to the diagrams at:

LC100 Workshop Manual - https://lc100e.github.io/
Scroll down to
Electrical Wiring Diagram
> RELAY LOCATIONS
> Instrument Panel
> [Pick vehicle year of interest]
– then open this page, scroll down to RHD and look for Suspension Control ECU

OR,

LC100 Workshop Manual - https://lc100e.github.io/
Scroll down to
Electrical Wiring Diagram
> RELAY LOCATIONS
> ELECTRICAL WIRING ROUTING [Parts]
> RHD Instrument Panel
> [Pick vehicle year of interest]
– then open this page and look for item A32 – AHC Main Relay (can be A33 on some models), the Suspension Control ECU is behind and attached to the AHC Main Relay

 

[Urtwob]

There is a picture at this link to Post #102 of the position of the Suspension Control ECU and AHC Main Relay in the Driver's footwell in a USA Left Hand Drive vehicle (the AHC Main Relay is missing in this example but the holder can be seen). This may help to visualise the Left Hand Drive situation.

Quick question about AHC ride with extra weight

Hey guys, I have a 2006 land cruiser and I like the ride on it for the most part but I feel I may be missing out on something due to having AHC problems. Everyone says the land cruisers ride like clouds, but its not all THAT smooth to me. It rides pretty good, but only slightly better than my...

forum.ih8mud.com

In your Right Hand Drive vehicle, the Suspension Control ECU and attached AHC Main Relay is in an analagous position on the left leg side of your Driver's footwell -- unless it has been moved during modifications.

Suggest probe above and slightly to the left of the DLC3 socket.

Also suggest go to the diagrams at:

LC100 Workshop Manual - https://lc100e.github.io/
Scroll down to
Electrical Wiring Diagram
> RELAY LOCATIONS
> Instrument Panel
> [Pick vehicle year of interest]
– then open this page, scroll down to RHD and look for Suspension Control ECU

OR,

LC100 Workshop Manual - https://lc100e.github.io/
Scroll down to
Electrical Wiring Diagram
> RELAY LOCATIONS
> ELECTRICAL WIRING ROUTING [Parts]
> RHD Instrument Panel
> [Pick vehicle year of interest]
– then open this page and look for item A32 – AHC Main Relay (can be A33 on some models), the Suspension Control ECU is behind and attached to the AHC Main Relay

Your a star @IndroCruise.

This vehicle was with another mechanic before it came to me.
I know he tried an ECU from an older LC100. He said it didn’t work or change / fix anything.
Crazy as it seems I’m getting suspicious the Cruiser may have arrived at my shop with No AHC ECU connected just now.
It’s a real pain to get at.
The owners husband had a disability kit installed, it’s actually brilliant.
Hand lever to side of steering wheel.
Push down = braking
Pull up = accelerating.
Great adaptation. But it blocks all access to beneath the Console and steering column.

No ECU attached!!
That would explain a lot!!!!!

I have since got the following error codes.
(Finally have learned how to read these BLINKING OFF lights )

Codes 31, 32, 33, 34, and 36, are all registering.

Have you any idea where I can read what each code means?

Thank you.

 

[IndroCruise]

Just to be sure there is no confusion .....

Production of LC100 ended in early 2007.

A 2007--2008 Land Cruiser would be LC200 -- with very different AHC system to LC100.

???

 

[Urtwob]

Just to be sure there is no confusion .....

Production of LC100 ended in early 2007.

A 2007--2008 Land Cruiser would be LC200 -- with very different AHC system to LC100.

???

You are “On the money” my friend.

The owner of the cruiser kept telling me it was a 2008 LC200

It is 100% definitely not.
I researched the fuse boxs and fuse box layouts for each model and year.

This is definitely a 2007 LC100 4.2 UK.
The fuse boxs under hood and kick side panel in cabin are identical to my LC100

This must-information was throwing me off course.

I have since found what all those codes are and they are all related to the AHC ECU.

Either it’s not there at all or it is not plugged in correctly.

Of course there is one more possibility, the ECU could be toast. Maybe one of the other technicians fried it before I got it. !!!

Anyway, thank you for your nudge with the technical manual, I found what those codes relate to and it does make sense to my investigation.

One other thing I found today, the 50amp AHC fuse in under the hood in main fuse box was blown. !!!

I will keep all informed.

Thank you @IndroCruise for your “as usual” masters touch.

 

[Urtwob]

You are “On the money” my friend.

The owner of the cruiser kept telling me it was a 2008 LC200

It is 100% definitely not.
I researched the fuse boxs and fuse box layouts for each model and year.

This is definitely a 2007 LC100 4.2 UK.
The fuse boxs under hood and kick side panel in cabin are identical to my LC100

This must-information was throwing me off course.

I have since found what all those codes are and they are all related to the AHC ECU.

Either it’s not there at all or it is not plugged in correctly.

Of course there is one more possibility, the ECU could be toast. Maybe one of the other technicians fried it before I got it. !!!

Anyway, thank you for your nudge with the technical manual, I found what those codes relate to and it does make sense to my investigation.

One other thing I found today, the 50amp AHC fuse in under the hood in main fuse box was blown. !!!

I will keep all informed.

Thank you @IndroCruise for your “as usual” masters touch.

 

[Urtwob]

Hi @IndroCruise, it’s quite a while since I have been on the forum.
I hope and trust you and all my other fellow forum members are keeping well.

Still working at the 2006 LC100, facelift model of my friends.

We have not yet succeeded in diagnosing what is wrong with the AHC.

It is sitting down on the bumps and the “off” blinking light is on from the instance you turn on the key.

So far all attempts at the active test have failed.
We have a major component failure in the system. It could be the ECU itself.

If you remember I discovered that the main 50amp AHC fuse in the fuse box beneath the hood was blown at a time.

It has not blown ever since, although the AHC has never worked ever since as well.

Perhaps you could help me with a small problem my friend.

I am at the point of going to try test all the wires going into and from the AHC ECU.

I believe I saw detsils of how to test the wires going into and out of, the AHC ECU.

If my memory is correct the data I was reading mentioned having to put the test probe of my meter down inside the sleeve of some of the input wires and then in other cases I could pull the plug out and put the test probe into certain ports on a certain plug.

I think in order to test if the ECU was getting power I have to keep the plugs plugged into the ECU and slide the probe needle down into the input wire sheath.

I’m waffling deliberately here Indrocruise, as I am trying to recall small bits of info from my memory in a hope it may prompt some one to recall or identify the data I was reading or am referring to,

I am 99% sure I was reading this material in the LC100 workshop manual however I have been trawling the workshop manual for hours and I cannot find the data I’m looking for.

I was certain I had made a note of it’s location on my “notes” but alas I cannot find that data either.

My quest is to test the ECU as best I can and to check the wires going into the ECU for signal and for any possible shorting of wires coming to the ECU.

I know it’s a big task, however having been unwell for quite a while I am now much better and I’m mentally geared up to have a go.

Thank you to everyone for having a read at this and I would appreciate any advice or guidance from you guys.