AHC – so slow, erratic, what to do next? Help requested please (1 Viewer)

[IndroCruise]

Hi All,

Firstly, apologies in advance for this long post. It attempts to describe a current issue as clearly as possible.

I have a longstanding and worsening AHC problem. Help is requested please from anywhere in the world ….

Despite refurbishments which have included lots of vital new parts, the AHC system on my 2006 LC100 steadfastly refuses to rise to any occasion from “LO” to “N” in anything much less than 38 seconds – after having dropped slowly from “N” to “LO” in 22 seconds.

And yet this vehicle will spring from “N” to “HI” in about 14 seconds on command – and then it is happy to drop back to “N” from “HI” in 8 seconds when required.

The Good Book (FSM) says that upwards movements “LO” to “N” or “N” to “HI” should each take about 15 seconds for a healthy system which has been correctly adjusted and is free of excess weight and other interferences and problems. Downwards movements should take 8 seconds or less.

In addition, the vehicle is erratic and does not settle reliably at the same expected front and rear hub-to-fender heights after an up or down movement or after a road trip.

It does not matter what adjustment I make to the Height Control Sensor adjusters, the vehicle resolutely insists on stopping at “N” from “LO” with Techstream (actually ELMscan327) readings of negative 4 to negative 8 millimetres – nowhere near zero!! It is different and a little better when dropping from “HI” to “N”. It is different again, sometimes with positive readings after returning home from a trip. Then, hub-to-fender distances also become a little higher, often half-inch or a little more, which must mean higher but immeasurable AHC pressures, guessing around 1.1 Mpa additional at the front.

The vehicle does maintain reliable and equal ‘cross level’ hub-to-fender distances within one-eighth of an inch (3 millimetres).

Shortly, my vehicle (see signature line) shortly will leave home on the East Coast of Australia and will be delivered to family members in Perth, Western Australia – about 4,300 kilometres (2,680 miles) away.

Naturally, I do not wish to hand over a ‘lemon’. Many very conservative and pre-emptive refurbishments have been undertaken. Some of these replacements of all new Toyota parts were made pre-emptively for longevity and reliability reasons rather than due to other specific adverse ‘symptoms’ -- in particular because it is easy in Australia to get good help on all Landcruiser matters except the mysteries of AHC/TEMS!! It was time for replacement of ‘globes’ and springs. It also was hoped that most issues also would be resolved by these efforts – but this has not happened. The above behaviour prevails even with some very new parts.

Specific details of the vehicle and suspension status include:

• Vehicle Age and mileage: built 06/2006, travelled 209,652 kilometres (130,271 miles),
• Model: HDJ100R-GNAEZQ “Sahara”, with 1HD-FTE turbodiesel, AHC/TEMS, ABS, A-TRAC, VSC, VGRS,
• Location: Brisbane, Australia,
• ‘Globes’: replaced 05/2019 (new Toyota parts), still showing today ~14 graduations at AHC Tank between “LO” and “HI”,
• FR, FL, and Rear Height Control Sensors: all replaced 07/2020 (new Toyota parts),
• AHC Pump Assembly (pump, motor, pressure and temperature sensors, tank): replaced 10/2020, (new Toyota parts),
• AHC Height Control Accumulator (long cylinder, includes new solenoid valve): replaced 10/2020 (new Toyota part),
• Front Suspension: ‘Sweaty’ Front ‘Shock Absorbers’ replaced 09/2016 (new Toyota parts), original Torsion Bars adjusted to correct Front AHC pressures, front wheel bearings replaced and bushes reviewed 05/2020, steering rack reconditioned 09/2019,
• Rear Suspension: Installed KING KTRS-79 Springs (no spacers) with Firestone airbag assist including Kevlar protectors inside coils 10/2019, also did small Rear Sensor Lift to partially offset low AHC pressures resulting from the higher spring rate of the new springs, also replaced rear LCA’s and rear UCA’s 09/2019,
• Last AHC Fluid change: 10/2020 (new genuine Toyota AHC Fluid 08886-01805),
• ARB Deluxe Front Bar with hoops (no winch) per avatar, KAYMAR single wheel carrier (not full bar), Toyota towbar,
• BFG 275/65R17 KO2 tyres, Load Rating “E”, set at 40 psi for highway cruising,
• Ride Quality and Comfort: Very Good – as expected, slightly firmer than stock especially when empty, due to choice of tyres and rear springs – but excellent when loaded for touring. Excellent response to COMFORT>>SPORT switch settings.

The first attachment is a Data Sheet which sets out details of tests and measurements carried out on 26th October 2020.

The vehicle sits a little low in these tests – raising the vehicle by pushing all Sensor adjusters up their slides has not improved the situation. Nor have attempts to bring the Sensor read-outs closer to zero where they should be. Instead the vehicle was raised and the negative Sensor readings persisted.

The second attachment shows “stills” from a video I made of the on-screen pressure changes during a “LO” to “N” rise of the vehicle. The videos were made as part of an effort to understand what the Levelling Valves in the Control Valve Assembly were doing and also, if possible, to confirm the operation of the solenoid valve on the Height Control Accumulator. (I am not sure what to make of the trace of the Height Control Accumulator pressure). The video file is too big to attach but the marked-up “stills” give the idea. They show the long response times and slow build-up of pressure. These solenoid valves in the Control Valve Assembly and the Height Control Accumulator have been checked by touch and sound and by the “Active Test” and do seem to be operating. Arthritic fingers have not yet succeeded in removing the electrical connectors and so resistances have not yet been checked per FSM, nor has continuity been checked through to the ECU. The new Height Control Sensors all operate correctly. Hopefully there are no blockages in the tiny filter “socks” inside the new AHC Pump! Underbody condition is excellent with no corrosion and no visible harness damage.

I have wondered whether there is mechanical interference somewhere, such as in the suspension bushings or between the airbags and their covers and the rear springs, when moving between “LO” and “N”. My Independent Mechanic thinks not. It all seems to work very well between “N” and “HI”.

Anyway, this is a long story with a lot of attached detail. All advice, comments, critique, ideas from anyone anywhere about what to do next would be most welcome. May I specifically tag @uHu, @PADDO, @LndXrsr, @Moridinbg, @2001LC, @suprarx7nut, whose insights on such matters always has been helpful.

 

[suprarx7nut]

Some comparison from a few others cars is probably needed here. Mine seems slow as well, but it's never been problematic. Your numbers are probably similar to mine.

I was going to suggest the pump is old, but if that's new, I'm not sure what else might be causing that slowness. Kinked line, maybe? Some sort of flow restriction?

 

[LndXrsr]

Indro, you're not the one who's supposed to have problems, you're supposed to be helping fix others' problems! If you're having trouble, this is going to be a difficult challenge for sure.

I'll say, my initial impressions regarding the slowness were: pump, debris in the lines (still possible even after a flush I suppose), and sensors. But you've done all those things and not with junk aftermarket parts.

Second, I don't think your sensor readings are that far off. Within 10mm of zero perhaps isn't "perfect" but it's in the realm of acceptable and 5mm or less is very good. You certainly aren't handing over an AHC lemon to your family with all these new parts and so much care and maintenance put in.

You are on the soft end of the rear pressures and given that more weight is supported by your stout rear springs, that may slow down the N-->L movement, but I would think would help speed up the L-->N process. If you wanted to be super thorough, you could swap stock springs back in and see if things change at all.

 

[LndXrsr]

Some comparison from a few others cars is probably needed here. Mine seems slow as well, but it's never been problematic. Your numbers are probably similar to mine.

I was going to suggest the pump is old, but if that's new, I'm not sure what else might be causing that slowness. Kinked line, maybe? Some sort of flow restriction?

As a comparator, my truck probably is close to the FSM 8 seconds from N-->L. 15-20sec L-->N. So I do think those times are quite long and represent something slightly goofy. At the same time, if it reliably goes into L, N, and H, I'm not sure the time, money, and effort to sort it out beyond what you've already done will net very good returns.

 

[ramangain]

Indro, if the ride is fine, and it cycles through all height changes consistently, does it matter if it takes a little longer?

 

[IndroCruise]

Hi All,

Firstly, apologies in advance for this long post. It attempts to describe a current issue as clearly as possible.

I have a longstanding and worsening AHC problem. Help is requested please from anywhere in the world ….

Despite refurbishments which have included lots of vital new parts, the AHC system on my 2006 LC100 steadfastly refuses to rise to any occasion from “LO” to “N” in anything much less than 38 seconds – after having dropped slowly from “N” to “LO” in 22 seconds.

And yet this vehicle will spring from “N” to “HI” in about 14 seconds on command – and then it is happy to drop back to “N” from “HI” in 8 seconds when required.

The Good Book (FSM) says that upwards movements “LO” to “N” or “N” to “HI” should each take about 15 seconds for a healthy system which has been correctly adjusted and is free of excess weight and other interferences and problems. Downwards movements should take 8 seconds or less.

In addition, the vehicle is erratic and does not settle reliably at the same expected front and rear hub-to-fender heights after an up or down movement or after a road trip.

It does not matter what adjustment I make to the Height Control Sensor adjusters, the vehicle resolutely insists on stopping at “N” from “LO” with Techstream (actually ELMscan327) readings of negative 4 to negative 8 millimetres – nowhere near zero!! It is different and a little better when dropping from “HI” to “N”. It is different again, sometimes with positive readings after returning home from a trip. Then, hub-to-fender distances also become a little higher, often half-inch or a little more, which must mean higher but immeasurable AHC pressures, guessing around 1.1 Mpa additional at the front.

The vehicle does maintain reliable and equal ‘cross level’ hub-to-fender distances within one-eighth of an inch (3 millimetres).

Shortly, my vehicle (see signature line) shortly will leave home on the East Coast of Australia and will be delivered to family members in Perth, Western Australia – about 4,300 kilometres (2,680 miles) away.

Naturally, I do not wish to hand over a ‘lemon’. Many very conservative and pre-emptive refurbishments have been undertaken. Some of these replacements of all new Toyota parts were made pre-emptively for longevity and reliability reasons rather than due to other specific adverse ‘symptoms’ -- in particular because it is easy in Australia to get good help on all Landcruiser matters except the mysteries of AHC/TEMS!! It was time for replacement of ‘globes’ and springs. It also was hoped that most issues also would be resolved by these efforts – but this has not happened. The above behaviour prevails even with some very new parts.

Specific details of the vehicle and suspension status include:

• Vehicle Age and mileage: built 06/2006, travelled 209,652 kilometres (130,271 miles),
• Model: HDJ100R-GNAEZQ “Sahara”, with 1HD-FTE turbodiesel, AHC/TEMS, ABS, A-TRAC, VSC, VGRS,
• Location: Brisbane, Australia,
• ‘Globes’: replaced 05/2019 (new Toyota parts), still showing today ~14 graduations at AHC Tank between “LO” and “HI”,
• FR, FL, and Rear Height Control Sensors: all replaced 07/2020 (new Toyota parts),
• AHC Pump Assembly (pump, motor, pressure and temperature sensors, tank): replaced 10/2020, (new Toyota parts),
• AHC Height Control Accumulator (long cylinder, includes new solenoid valve): replaced 10/2020 (new Toyota part),
• Front Suspension: ‘Sweaty’ Front ‘Shock Absorbers’ replaced 09/2016 (new Toyota parts), original Torsion Bars adjusted to correct Front AHC pressures, front wheel bearings replaced and bushes reviewed 05/2020, steering rack reconditioned 09/2019,
• Rear Suspension: Installed KING KTRS-79 Springs (no spacers) with Firestone airbag assist including Kevlar protectors inside coils 10/2019, also did small Rear Sensor Lift to partially offset low AHC pressures resulting from the higher spring rate of the new springs, also replaced rear LCA’s and rear UCA’s 09/2019,
• Last AHC Fluid change: 10/2020 (new genuine Toyota AHC Fluid 08886-01805),
• ARB Deluxe Front Bar with hoops (no winch) per avatar, KAYMAR single wheel carrier (not full bar), Toyota towbar,
• BFG 275/65R17 KO2 tyres, Load Rating “E”, set at 40 psi for highway cruising,
• Ride Quality and Comfort: Very Good – as expected, slightly firmer than stock especially when empty, due to choice of tyres and rear springs – but excellent when loaded for touring. Excellent response to COMFORT>>SPORT switch settings.

The first attachment is a Data Sheet which sets out details of tests and measurements carried out on 26th October 2020.

The vehicle sits a little low in these tests – raising the vehicle by pushing all Sensor adjusters up their slides has not improved the situation. Nor have attempts to bring the Sensor read-outs closer to zero where they should be. Instead the vehicle was raised and the negative Sensor readings persisted.

The second attachment shows “stills” from a video I made of the on-screen pressure changes during a “LO” to “N” rise of the vehicle. The videos were made as part of an effort to understand what the Levelling Valves in the Control Valve Assembly were doing and also, if possible, to confirm the operation of the solenoid valve on the Height Control Accumulator. (I am not sure what to make of the trace of the Height Control Accumulator pressure). The video file is too big to attach but the marked-up “stills” give the idea. They show the long response times and slow build-up of pressure. These solenoid valves in the Control Valve Assembly and the Height Control Accumulator have been checked by touch and sound and by the “Active Test” and do seem to be operating. Arthritic fingers have not yet succeeded in removing the electrical connectors and so resistances have not yet been checked per FSM, nor has continuity been checked through to the ECU. The new Height Control Sensors all operate correctly. Hopefully there are no blockages in the tiny filter “socks” inside the new AHC Pump! Underbody condition is excellent with no corrosion and no visible harness damage.

I have wondered whether there is mechanical interference somewhere, such as in the suspension bushings or between the airbags and their covers and the rear springs, when moving between “LO” and “N”. My Independent Mechanic thinks not. It all seems to work very well between “N” and “HI”.

Anyway, this is a long story with a lot of attached detail. All advice, comments, critique, ideas from anyone anywhere about what to do next would be most welcome. May I specifically tag @uHu, @PADDO, @LndXrsr, @Moridinbg, @2001LC, @suprarx7nut, whose insights on such matters always has been helpful.

Thank you all for comments so far. Probably @ramangain is right! However, my well-cultivated obsessive-compulsive inner self was not quite ready to let me to concede, so I kept looking for the ‘cause’ of the current ‘effects’ ….

No physical adjustments have been made since the previous tests and measurements which were done on 26th October 2020, as set out on the Data Sheet attached to Post #1 in this thread.

On return from a short trip, I noticed that the car was sitting a little higher.

Started engine again, drove out of the garage, then back in, just to be sure that the AHC system and pump had finished doing their thing and that the suspension had settled. While the engine was still running with AHC “ON”, measured all hub-to-fender distances (to the nearest one-eighth inch):

FR hub-to-fender: 19.875 inches (previously, after LO>> N: 19.250 inches)
FL hub-to-fender: 20.000 inches (previously, after LO>> N: 19.250 inches)
RR hub-to-fender: 20.875 inches (previously, after LO>> N: 20.500 inches)
RL hub-to-fender: 20.750 inches (previously, after LO>> N: 20.500 inches)

FR Height Control Sensor: +11.4 millimetres (previously, after LO>> N): – 5.0 millimetres
FL Height Control Sensor: +12.4 millimetres (previously, after LO>> N): – 4.2 millimetres
Rear Height Control Sensor: – 2.8 millimetres (previously, after LO>> N): – 8.0 millimetres

Mmmmm – confusion! This is a long, long way different to my previous measurements N >> LO >> N following the FSM procedure. What should be made of the above height differences and sensor differences? Why does this happen? Does it simply mean that this is where the suspension landed at the time the vehicle has stopped at engine OFF but that suspension has not yet ‘self-levelled’?

However, this situation happens repeatedly.

The ‘control loop’ should result in the ECU causing the suspension to stop at or close to zero height sensor readings (possibly with minor adjustable differences between sensors to allow for manufacturing differences, wear and tear differences, etc). This is the design. It should happen regardless of the actual hub-to-fender operational height setting chosen by the Owner, provided that system faults or Owner errors have not caused the ECU to override with ‘fail-safe’ settings as defined in the FSM. Note: The Height Control Sensors are new.

No Diagnostic Trouble Codes (DTC’s) are present. On the road, the system feels normal and behaves normally. Physical responses to the four-position COMFORT >> SPORT console switch are good, the Front and Rear Wheel Step positions are visible on the read-out, also the variations with each console switch positions on the read-out can be seen while moving. The different combinations of the Damper Force Switches also can be seen on the read-out screen. (For these purposes, I attach the screen to the windscreen for observation purposes while the vehicle is moving).

No physical AHC/TEMS ‘fail safe’ symptoms are present.

Drove out of the garage, around the local streets and back into the garage. With engine and AHC still “ON”, got out of the vehicle and re-measured. The high operating hub-to-fender measurements and the high sensor readings were much the same as recorded above.

What does it mean for front and rear AHC pressures at these increased heights? How can these be measured in real time?

What the hell, I thought, let’s do another N >> LO >> N height movement per FSM and measure everything yet again! This resulted in the following: (tape measurements to nearest one-eighth inch)

Times: N >> LO: 21 seconds and LO >> N: 38 seconds (both similar to the very long times in previous measurements on 26th October 2020)

This time, with my head poised over the AHC Pump, I noticed that the pump started immediately that the LO >> N raise began (when I closed the vehicle door).

I could not tell whether pump operation was as well as, or instead of, the Height Control Accumulator releasing its pressure to initiate the raise, as it should do when fully charged and raising from LO to N. The Height Control Accumulator and its attached Solenoid Valve are new. The AHC Pump continued throughout this long duration raise until the dashboard light stopped blinking and remained steady at N and then continued for another 15 seconds (timed).

I waited another 60 seconds with engine running, then measured ….

FR hub-to-fender: 19.125 inches (previously, after LO>> N): 19.250 inches
FL hub-to-fender: 19.250 inches (previously, after LO>> N): 19.250 inches
RR hub-to-fender: 20.500 inches (previously, after LO>> N): 20.500 inches
RL hub-to-fender: 20.625 inches (previously, after LO>> N): 20.500 inches

…. and Techstream (ELMscan327) readings:

FR Height Control Sensor: – 4.6 millimetres (previously, after LO>> N: – 5.0 millimetres)
FL Height Control Sensor: – 5.0 millimetres (previously, after LO>> N: – 4.2 millimetres)
Rear Height Control Sensor: –7.6 millimetres (previously, after LO>> N: – 8.0 millimetres)

Front Pressure: 6.9MPa; Rear Pressure: 5.8 MPa (previously, after LO>> N: Front: 6.9 MPa; Rear: 5.7 MPa)

Mmmm – back to where we were. These new, timed, tape-measured and re-tested N >> LO >> N results are all reasonably consistent with the earlier N >> LO >> N results on 26th October 2020 as shown on the Data Sheet attached to Post #1 in this thread.

Then I thought, for the last experiment of the weekend, let’s see what happens when the pressures and heights build while on the move, instead of the static situation in the garage in the conditions prescribed by FSM. This meant that, different to all previous tests, I would be in the vehicle.

With vehicle stopped on a level road, dropped height to LO. Started Techstream (ELMscan327) and drove at 10 kilometres per hour (6 miles per hour), until vehicle raised to N and dashboard light stopped blinking. (FSM states that “When the vehicle height is at LO, vehicle is automatically raised to N when the vehicle speed becomes higher than 5 kilometres per hour (3 miles per hour). At this time, the fluid stored in the Height Control Accumulator also is used”. I could hear the AHC Pump running, maybe recharging the accumulator). Note: The AHC Pump Assembly and the Height Control Accumulator are new.

Return to garage, engine still ON, got out of the vehicle to re-measure hub-to-fender distances:

Tape measurements (to nearest one-eighth inch):

FR hub-to-fender: 19.750 inches
FL hub-to-fender: 19.750 inches
RR hub-to-fender: 20.875 inches
RL hub-to-fender: 20.875 inches

Techstream (ELMscan327) readout (engine still ON, driver now out of vehicle):

Again, all very different to the N >> LO >> N static tests as prescribed by FSM and as repeated several times and recorded above. This time the Front Sensor readings are positive and the Rear Sensor reading is slightly negative. Uncertain whether the higher Front and Rear AHC pressures in this read-out are due to the greater heights, or my presence in the vehicle, or both.

Investigations continue.

As previously, all comments and advice are welcome.

 

[ramangain]

1. Is your gas tank full?
2. What does FSM say about averages for height sensor readings?
3. Hub to fender heights are not in the FSM are they?

Mountains from mole hills amigo

 

[thebeedeegee]

For a comparison my 1999 LX with 186k miles takes about 5 seconds from N to L, then another 5 to 6 from L to N. It took about 8 seconds to go from N to H.

I have a front bumper only

 

[uHu]

Two causes for slow N-L-N that I have observed:
One - is if a sensor (or more) is bad, giving a varying signal, the system can take a long time finding out "where it is". This seems unlikely in your case.
The second - is if the height is adjusted too low, or if the car is parked so that the rear right wheel is higher than the left (sensor is towards left side), it will have problems reaching normal Lo height. It will lower the pressure a bit extra, as much as possible, and at the end give up and say "OK, this is Lo", even if it isn't as low as Lo normally is. In those cases I see that it also takes a long time before it starts moving up again, towards N. It might have to do with a lower pressure than standard at position Lo, and therefore more fluid to pump. Having King Springs could do a bit of the same, making it more difficult to reach Lo. You could test the theory by setting the rear height higher by an inch or more, so that it will easier reach the sensor's Lo position.

 

[LndXrsr]

I'll agree with uHu that you have bad sensor symptoms (widely varying sensor height readings on Tachstream), but with new OEM sensors. I'd double check the plugs and wiring to the sensors seems solid. Any intermittent shorts might result in findings similar a bad sensor, even though the sensor itself is okay.

 

[albylam]

I'll agree with uHu that you have bad sensor symptoms (widely varying sensor height readings on Tachstream), but with new OEM sensors. I'd double check the plugs and wiring to the sensors seems solid. Any intermittent shorts might result in findings similar a bad sensor, even though the sensor itself is okay.

Did you ever find the problem? After my flush I am getting a similar problem. There doesn't seem to be a diagnostic if n to l is above the standard time of 15 seconds.. not sure if this needs to be addressed

 

[IndroCruise]

Did you ever find the problem? After my flush I am getting a similar problem. There doesn't seem to be a diagnostic if n to l is above the standard time of 15 seconds.. not sure if this needs to be addressed

@albylam -- as you have recognised, this is “unfinished business” in my case. It is a long story. Some explanation is owed to those who have tried to help previously. These notes also may be of assistance to others ….

As a result of internal family arrangements, my LC100 was shipped by sea from Brisbane around southern Australia to Perth in late November 2020, before the outstanding problems were resolved.

Plans to drive the vehicle 4,300 road kilometres (2,670 miles) across four States had been frustrated by various COVID-related State Border Closures by State Governments in Australia at that time.

The idea was that during a subsequent visit to Perth, I would resolve all ongoing issues and introduce my son-in-law to the inner workings of AHC and TEMS systems.

Other family obligations and various further COVID-related lockdowns by State Governments have meant that this visit and AHC problem resolution STILL have not taken place!!

FRUSTRATION+++! But a visit is now planned for September 2021 ….

I am not complaining. While the strict approach in Australia to international and interstate COVID-related border controls have been controversial at times, Australia has benefitted from remarkably low incidence of COVID cases and deaths.

Anyway, back to the vehicle and details by way of background ….

As part of the internal family arrangements, various components of the AHC system were replaced with new Toyota/Lexus OEM parts. The aim was (and remains) to ensure longevity of this 15 years old 2006 vehicle to at least 500,000 kilometres (more than 300,000 miles). It is very well maintained and is in excellent rust-free condition after only 210,000 kilometres (130,000 miles) in the relatively hot, dry Australian continent. The vehicle is powered by the long-living 1HD-FTE 4.2 litre 6-cylinder turbodiesel engine.

Previous AHC-related replacements over the last few years were aimed at long term reliability. These included:

• AHC Pump Assembly -- including Pump, Motor, Pressure Sensor, Temperature Sensor, Tank, etc, but not including the Attenuator located below the Pump, before the Control Valve Assembly,
• Height Control Accumulator including solenoid valve,
• All four Gas Chambers (Front and Rear), a.k.a. ‘globes’ -- but not including Damping Force Control Actuators,
• Front ‘Shock Absorbers’ due to high pressure leakage but not Rear ‘Shock Absorbers’ which have never leaked,
• All Height Control Sensors (Front Left, Front Right, and Rear),

The main vehicle enhancements and/or weight additions are:

• ARB Deluxe Bar 3413190 at front – without winch,
• KAYMAR single wheel carrier,
• Toyota standard tow bar,
• KTRS-79 rear coil springs,
• Airbags inside rear springs – high pressure Firestone Coilrite with Kevlar sleeves,
• BFG275/65R17 121/118S KO2 “E” rated tyres on OEM 17” wheels.

The responses to my original call for help from @suprarx7nut, @LndXrsr, @ramangain, @uHu are acknowledged again -- thank you.

The vehicle has remained driveable and ride quality is good – but the previously reported inconsistent behaviours concerning heights and pressures remain unresolved.

When I finally get to Perth from Brisbane and get re-acquainted with this vehicle in September, then there will be a “back to basics” effort. This will be done personally -- unless someone is found in Perth who really knows and understands the AHC/TEMS systems on LC100/LX470 and can do it for me – but such persons are rare:

1. Bleed AHC again at all four ‘globes’ and at Height Control Accumulator [all should be OK, done twice in October 2020 by my Independent Mechanic, but this time I will do it personally to eliminate any doubts about air in the system],
2. Remove and test all Height Control Sensors per FSM, also check connectors at Sensors, also check harness for continuity and voltage supply back to next connector [on top of wheel-arch in case of Front Sensor Harnesses, have to find similar further back connector/checkpoint for Rear Sensor Harness or check at ECU],
3. Cross-level front [always good on this vehicle but check again anyway],
4. Set vehicle hub-to-fender heights [“Active Test” will be used to re-set vehicle hub-to-fender distances a.k.a. ‘ride heights’: Front 19.50 inches (500 millimetres), Rear 20.50 inches (520 millimetres)],
5. Re-set Height Sensor readings as near as possible to zero on Techstream (or Elmscan327) scanner when hub-to-fender 'ride heights' are correct [suspect that Sensors may not have been set correctly to near-zero when last at Independent Workshop],
6. Test and record Front, Rear and Accumulator AHC pressures [adjust Front Pressures as necessary with Torsion Bar adjusters, maybe add some “sensor lift” at rear to offset some of the pressure reduction caused by KTRS-79 springs],
7. Road test and “fine tune” all height and pressure adjustments,
8. Test and record LO>>N and N>>HI raise times compared to FSM,

If after these "back to basics" checks the inconsistent height problems and very slow-to-raise problems still continue as reported previously, then these may point to issues at the AHC Pump even though it is new (!) – thinking partial blockages at the particle strainers inside the actual Pump or at the Return Valve, caused by residues of old AHC Fluid, detritus in the system, etc, possibly causing insufficient pressure and flow to complete LO >> N raise. It is annoying and frustrating to dis-assemble a new AHC Pump but the work is not difficult. See some pics at Post #67 through to Post #70 at this thread:
AHC pump out? - https://forum.ih8mud.com/threads/ahc-pump-out.1226629/page-4#post-13401098

Incorrect voltages from Height Control Sensors may not show as a DTC unless there is an open circuit or a short circuit – so mere absence of Height Control Sensor DTC’s can never be taken as assurance of good health of these Sensors. Worn Sensors, corrosion, or other causes of "scratchy" or erratic signals or inconsistencies between Sensors may be present without a DTC being recorded. Reliable signals from Height Control Sensors are vital to AHC/TEMS performance -- so electrical checks of Sensors per FSM are important.

Findings will be reported when some progress is made.

References:

AHC/TEMS GENERAL DESCRIPTION AND GUIDANCE ON LOAD LIMITS:
https://lc100e.github.io/manual/, then tabs
New Car Features > CHASSIS > Suspension > Active Height Control Suspension and Skyhook TEMS

ON-VEHICLE INSPECTION:
https://lc100e.github.io/manual/, then tabs
Repair Manual > SUSPENSION AND AXLE > Active Height Control System (Independent Front Suspension) > ON-VEHICLE INSPECTION

AHC/TEMS DIAGNOSTICS:
https://lc100e.github.io/manual/, then tabs
Repair Manual > DIAGNOSTICS > ACTIVE HEIGHT CONTROL SUSPENSION & SKYHOOK TEMS

My geography for those interested:

 

[albylam]

Thank you @IndroCruise for all your contributions on this forum.

I finally had a chance and switched back the front right side sensor back to my old 20 year old oem sensor. (I had changed all my height sensors originally as I thought I was doing myself some preventative maintenance)

So before I was getting 30 to 40 seconds changing heights from N to L and L to N with my new sensors and now after reinstalling back my old right height sensor , I am all under 15 seconds. I am not sure whether the dorman sensor was faulty or if I bought the wrong dorman light sensor level or my connection was loose but I will monitor it for the next few days.

There was no change in weather conditions nor did I do any other Ahc flushes or service to my vehicle.

So today:
14 graduations,
L to N less than 15 sec
N to H less than 15 sec
H to N 5 sec
N to L 12 sec
10.4
7.6 front ( ill check again and adjust after a drive)
5.9 rear
Front height 530mm (techstream says im within spec for height but I dont know why my physical height is so high, maybe it will settle after a drive)
Rear heights 500mm

Anyways thank you for your advice

 

[parkeyjack]

@albylam -- as you have recognised, this is “unfinished business” in my case. It is a long story. Some explanation is owed to those who have tried to help previously. These notes also may be of assistance to others ….

As a result of internal family arrangements, my LC100 was shipped by sea from Brisbane around southern Australia to Perth in late November 2020, before the outstanding problems were resolved.

Plans to drive the vehicle 4,300 road kilometres (2,670 miles) across four States had been frustrated by various COVID-related State Border Closures by State Governments in Australia at that time.

The idea was that during a subsequent visit to Perth, I would resolve all ongoing issues and introduce my son-in-law to the inner workings of AHC and TEMS systems.

Other family obligations and various further COVID-related lockdowns by State Governments have meant that this visit and AHC problem resolution STILL have not taken place!!

FRUSTRATION+++! But a visit is now planned for September 2021 ….

I am not complaining. While the strict approach in Australia to international and interstate COVID-related border controls have been controversial at times, Australia has benefitted from remarkably low incidence of COVID cases and deaths.

Anyway, back to the vehicle and details by way of background ….

As part of the internal family arrangements, various components of the AHC system were replaced with new Toyota/Lexus OEM parts. The aim was (and remains) to ensure longevity of this 15 years old 2006 vehicle to at least 500,000 kilometres (more than 300,000 miles). It is very well maintained and is in excellent rust-free condition after only 210,000 kilometres (130,000 miles) in the relatively hot, dry Australian continent. The vehicle is powered by the long-living 1HD-FTE 4.2 litre 6-cylinder turbodiesel engine.

Previous AHC-related replacements over the last few years were aimed at long term reliability. These included:

• AHC Pump Assembly -- including Pump, Motor, Pressure Sensor, Temperature Sensor, Tank, etc, but not including the Attenuator located below the Pump, before the Control Valve Assembly,
• Height Control Accumulator including solenoid valve,
• All four Gas Chambers (Front and Rear), a.k.a. ‘globes’ -- but not including Damping Force Control Actuators,
• Front ‘Shock Absorbers’ due to high pressure leakage but not Rear ‘Shock Absorbers’ which have never leaked,
• All Height Control Sensors (Front Left, Front Right, and Rear),

The main vehicle enhancements and/or weight additions are:

• ARB Deluxe Bar 3413190 at front – without winch,
• KAYMAR single wheel carrier,
• Toyota standard tow bar,
• KTRS-79 rear coil springs,
• Airbags inside rear springs – high pressure Firestone Coilrite with Kevlar sleeves,
• BFG275/65R17 121/118S KO2 “E” rated tyres on OEM 17” wheels.

The responses to my original call for help from @suprarx7nut, @LndXrsr, @ramangain, @uHu are acknowledged again -- thank you.

The vehicle has remained driveable and ride quality is good – but the previously reported inconsistent behaviours concerning heights and pressures remain unresolved.

When I finally get to Perth from Brisbane and get re-acquainted with this vehicle in September, then there will be a “back to basics” effort. This will be done personally -- unless someone is found in Perth who really knows and understands the AHC/TEMS systems on LC100/LX470 and can do it for me – but such persons are rare:

1. Bleed AHC again at all four ‘globes’ and at Height Control Accumulator [all should be OK, done twice in October 2020 by my Independent Mechanic, but this time I will do it personally to eliminate any doubts about air in the system],
2. Remove and test all Height Control Sensors per FSM, also check connectors at Sensors, also check harness for continuity and voltage supply back to next connector [on top of wheel-arch in case of Front Sensor Harnesses, have to find similar further back connector/checkpoint for Rear Sensor Harness or check at ECU],
3. Cross-level front [always good on this vehicle but check again anyway],
4. Set vehicle hub-to-fender heights [“Active Test” will be used to re-set vehicle hub-to-fender distances a.k.a. ‘ride heights’: Front 19.50 inches (500 millimetres), Rear 20.50 inches (520 millimetres)],
5. Re-set Height Sensor readings as near as possible to zero on Techstream (or Elmscan327) scanner when hub-to-fender 'ride heights' are correct [suspect that Sensors may not have been set correctly to near-zero when last at Independent Workshop],
6. Test and record Front, Rear and Accumulator AHC pressures [adjust Front Pressures as necessary with Torsion Bar adjusters, maybe add some “sensor lift” at rear to offset some of the pressure reduction caused by KTRS-79 springs],
7. Road test and “fine tune” all height and pressure adjustments,
8. Test and record LO>>N and N>>HI raise times compared to FSM,

If after these "back to basics" checks the inconsistent height problems and very slow-to-raise problems still continue as reported previously, then these may point to issues at the AHC Pump even though it is new (!) – thinking partial blockages at the particle strainers inside the actual Pump or at the Return Valve, caused by residues of old AHC Fluid, detritus in the system, etc, possibly causing insufficient pressure and flow to complete LO >> N raise. It is annoying and frustrating to dis-assemble a new AHC Pump but the work is not difficult. See some pics at Post #67 through to Post #70 at this thread:
AHC pump out? - https://forum.ih8mud.com/threads/ahc-pump-out.1226629/page-4#post-13401098

Incorrect voltages from Height Control Sensors may not show as a DTC unless there is an open circuit or a short circuit – so mere absence of Height Control Sensor DTC’s can never be taken as assurance of good health of these Sensors. Worn Sensors, corrosion, or other causes of "scratchy" or erratic signals or inconsistencies between Sensors may be present without a DTC being recorded. Reliable signals from Height Control Sensors are vital to AHC/TEMS performance -- so electrical checks of Sensors per FSM are important.

Findings will be reported when some progress is made.

References:

AHC/TEMS GENERAL DESCRIPTION AND GUIDANCE ON LOAD LIMITS:
https://lc100e.github.io/manual/, then tabs
New Car Features > CHASSIS > Suspension > Active Height Control Suspension and Skyhook TEMS

ON-VEHICLE INSPECTION:
https://lc100e.github.io/manual/, then tabs
Repair Manual > SUSPENSION AND AXLE > Active Height Control System (Independent Front Suspension) > ON-VEHICLE INSPECTION

AHC/TEMS DIAGNOSTICS:
https://lc100e.github.io/manual/, then tabs
Repair Manual > DIAGNOSTICS > ACTIVE HEIGHT CONTROL SUSPENSION & SKYHOOK TEMS

My geography for those interested:

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Hey there Indro. Thank your so much for all your contributions. I too am having the same problem. 30 seconds. Sometimes a bit less from L to N. 15 seconds to go from N to L. Just pulled my pump and reflushed the system. All new globes. Did a slight sensor lift in the rear and front after adding king springs. Front pressures are in spec rear is a bit under pressured due to the king springs and no extra weight. Let us know what the solution is. My ride is perfect but I too am a bit OCD when it comes to things and my cruiser. 181k miles on 2007 LC. Thanks again for the detailed post.