AHC Inop after fluid change 2007 lx C1751 and C1762 (3 Viewers)

[LndXrsr]

Just tuning in on this. Big bummer, sorry man. I would tend to agree with most of the recent recs on here to clean the pump if at all possible or if time is more valuable than money, source a new/used pump that's known to function. Would also agree that your AHC relay seems okay.

Accumulators are known to go bad occasionally, but I don't think that explains your symptoms at this point, so would reserve that for later.

This all makes me wonder if AHC flushes risk dislodging gunk or damaging seals in the way that aggressive trans flushes can mess with clutch plates and power steering flushes sometimes lead to new leaks. Still going to flush mine regularly for what it's worth.

 

[aharlan001]

I don't know if this means anything to anyone but. I am able to trick it into staying illuminated at N. If I turn the truck off when it is attempting to go from l to n and then turn the truck back on n is illuminated. I drove it to work like this about a 10 min drive and it stayed at N. Suspension felt ok as far as I can tell. I can't check techstream till late tonight but I did measure from fender to the center of the wheelcaps and I'm getting 19.25 on the front (spec is 19.75) and 20.25 in the rear (spec is 20.5) curious to see what my height sensor readings are...

 

[2001LC]

19.25 & 20.25" is typically what I find. This is not likely from low pressure, in AHC system. You may have had low voltage coming from battery and or weak pump due to gunk in reservoir/pump.

 

[aharlan001]

19.25 & 20.25" is typically what I find. This is not likely from low pressure, in AHC system. You may have had low voltage coming from battery and or weak pump due to gunk in reservoir/pump.

Interesting. So I guess thinks to try on the voltage front would be drive it to get the battery charged up, trickle charger overnight, battery testing, and swap the battery from my 98 lc. Glad I didnt sell it before I got this one baselined!

 

[IndroCruise]

Not yet only one I have is for 98 lc

The replies already given in this thread provide most of the relevant information. If you have not previously seen the FSM link below, it is worth a look because it has sections for most LC100 model years including the various combinations of engines and transmissions in USA and elsewhere. There is so much commonality with the LX470 that the differences do not matter except for bodywork, trim and accessory details.

On AHC matters, there are three places which can be helpful. These are:

A General Description of the Active Height Control (AHC) and Toyota Electronic Modulated Suspension (TEMS) systems and how they are meant to work. This 20-page description has good diagrams and explanations of each of the component parts of these systems. The hydraulic circuit diagrams are helpful when trying to visualise issues. This section is descriptive rather than diagnostic. It is worth printing for a careful read and later reference. This General Description is found easily at

https://lc100e.github.io/manual/

then follow the index tabs starting right at the top:
New Car Features > CHASSIS > Suspension > Active Height Control Suspension.

AHC/TEMS Diagnostics is a very important section and diagnostics are well-covered at the same FSM link -- https://lc100e.github.io/manual/ -- via these tabs:

Repair Manual > DIAGNOSTICS > ACTIVE HEIGHT CONTROL SUSPENSION & SKYHOOK TEMS

This section takes you to the Diagnostic Trouble Codes (DTC's) you are seeing. The "Problems Symptoms Table" also can be useful.

The “On-Vehicle Inspection” and “Adjustment” sections contain most of the AHC/TEMS procedures and specifications for setting up or adjusting the suspension. These are found at the same FSM link -- https://lc100e.github.io/manual/ -- via these tabs:

Repair Manual > SUSPENSION AND AXLE > ACTIVE HEIGHT CONTROL SYSTEM > ON-VEHICLE INSPECTION

Repair Manual > SUSPENSION AND AXLE > ACTIVE HEIGHT CONTROL SYSTEM > ADJUSTMENT

It is not relevant to your current issues but this last section includes the actual FSM vehicle operating height specifications. This are quite finnicky to measure. Instead, IH8MUD Members including @PADDO have recommended the following well-known operating height approximations for vehicles in as-built stock condition:

Front operating hub-to-fender distance: 19.75 inches (about 500 millimetres)

Rear operating hub-to-fender distance: 20.50 inches (about 520 millimetres)

These measurements are independent of tyre size but will be different if the vehicle has been ‘lifted’.

It is very late here -- 12:53 am Tuesday morning -- tomorrow I will have some time to read through this thread and possibly offer some further thoughts.

 

[LXKevin]

Looking for clues

POST # 38 this thread-
@aharlan001 answering questions from @2001LC regarding vehicle config/condition & AHC system condition pre-flush.

@aharlan001 states " Fluid fluid blead out was initially white with bubbles then yellow with tiny bubbles now light red no bubbles".

was this system running hydraulic or brake fluid? what's yellow? dirty white fluid turns yellow? What damage if any could we expect to see using brake fluid, hydraulic fluid, or some combo in the AHC system? @2001LC @uHu

 

[aharlan001]

The replies already given in this thread provide most of the relevant information. If you have not previously seen the FSM link below, it is worth a look because it has sections for most LC100 model years including the various combinations of engines and transmissions in USA and elsewhere. There is so much commonality with the LX470 that the differences do not matter except for bodywork, trim and accessory details.

On AHC matters, there are three places which can be helpful. These are:

A General Description of the Active Height Control (AHC) and Toyota Electronic Modulated Suspension (TEMS) systems and how they are meant to work. This 20-page description has good diagrams and explanations of each of the component parts of these systems. The hydraulic circuit diagrams are helpful when trying to visualise issues. This section is descriptive rather than diagnostic. It is worth printing for a careful read and later reference. This General Description is found easily at

https://lc100e.github.io/manual/

then follow the index tabs starting right at the top:
New Car Features > CHASSIS > Suspension > Active Height Control Suspension.

AHC/TEMS Diagnostics is a very important section and diagnostics are well-covered at the same FSM link -- https://lc100e.github.io/manual/ -- via these tabs:

Repair Manual > DIAGNOSTICS > ACTIVE HEIGHT CONTROL SUSPENSION & SKYHOOK TEMS

This section takes you to the Diagnostic Trouble Codes (DTC's) you are seeing. The "Problems Symptoms Table" also can be useful.

The “On-Vehicle Inspection” and “Adjustment” sections contain most of the AHC/TEMS procedures and specifications for setting up or adjusting the suspension. These are found at the same FSM link -- https://lc100e.github.io/manual/ -- via these tabs:

Repair Manual > SUSPENSION AND AXLE > ACTIVE HEIGHT CONTROL SYSTEM > ON-VEHICLE INSPECTION

Repair Manual > SUSPENSION AND AXLE > ACTIVE HEIGHT CONTROL SYSTEM > ADJUSTMENT

It is not relevant to your current issues but this last section includes the actual FSM vehicle operating height specifications. This are quite finnicky to measure. Instead, IH8MUD Members including @PADDO have recommended the following well-known operating height approximations for vehicles in as-built stock condition:

Front operating hub-to-fender distance: 19.75 inches (about 500 millimetres)

Rear operating hub-to-fender distance: 20.50 inches (about 520 millimetres)

These measurements are independent of tyre size but will be different if the vehicle has been ‘lifted’.

It is very late here -- 12:53 am Tuesday morning -- tomorrow I will have some time to read through this thread and possibly offer some further thoughts.

Looking for clues

POST # 38 this thread-
@aharlan001 answering questions from @2001LC regarding vehicle config/condition & AHC system condition pre-flush.

@aharlan001 states " Fluid fluid blead out was initially white with bubbles then yellow with tiny bubbles now light red no bubbles".

was this system running hydraulic or brake fluid? what's yellow? dirty white fluid turns yellow? What damage if any could we expect to see using brake fluid, hydraulic fluid, or some combo in the AHC system? @2001LC @uHu

Once the bubles cleared it looked like brake fluid. I have tons of records, every oil change religiously every 3k miles, tire rotation, timing belt, transmission fluid, multiple brake fluid flushes (way more than I would expect)... The differential/transfer case/drive shaft/suspension were never touched as far as I can tell. I can see maybe this guy topping off the ahc with brake fluid but I doubt it. Or maybe the oil change shop he went to topped it with brake fluid not knowing what they were doing. I can take a sample pic of the first liter and the second liter maybe tonight.

 

[LXKevin]

@aharlan001 Do you remember the order of your original bleed? Globes first? Accumulator first? At what point did you bleed the accumulator the first time?

 

[aharlan001]

Blead in l with truck off, Accumulator first, then left globes, start truck, recheck fluid in reservoir it was about at the seam, took an extra long time to go from l to n. Took it back down to l. Then truck off for short bleed of passenger side globes.

 

[ramangain]

If the fluid was not pinkish, or pinkish getting dirty (grey, brown, nasty) when you first started bleeding, then the wrong fluid was in your system (read: not Mr. T AHC fluid).

Are you 1000000000% sure that there is no chance air got introduced into the system, either via running the resevoir dry or leaving a bleed valve cracked open without the AHC system running?

 

[aharlan001]

100% sure the reservoir never ran dry. When I blead the accumulator the first time I had trouble getting it closed, air could have gotten in there. The hose fell off the bleeder and I had trouble getting it closed with fluid getting everywhere.

 

[aharlan001]

On subsequent blead attempts I got little to nothing from the accumulator bleeder.

 

[suprarx7nut]

100% sure the reservoir never ran dry. When I blead the accumulator the first time I had trouble getting it closed, air could have gotten in there. The hose fell off the bleeder and I had trouble getting it closed with fluid getting everywhere.

On subsequent blead attempts I got little to nothing from the accumulator bleeder.

I'm also curious on the fluid color. Non-pink is trouble.

On the accumulator getting air in it, I don't think that should be a problem. The system should be able to bleed air in any part of it.

If you run the active test from techstream, can you keep the vehicle pumping while you crack open the accumulator breather? Logistically that might be a challenge, but I think that would be worthwhile. If the pump can be verified to run while the bleeder is open, you should have fluid coming out. If you can't get that to happen, it seems like there's a bad clog or the pump is worn dead.

 

[LXKevin]

Looking for clues


Remember the active test?
Yesterday at 12:21 PM post #40
Always happy to try something new. So with each test on lit up for about 1 second. With main relay, motor relay, front leveling solenoid, rear leveling solenoid I could actually hear something happening when it was activated. With accumulator solenoid, front gate solenoid, and rear gate solenoid I heard nothing... not sure what this means... ------------------------------GREAT QUESTION?

So we did test height accumulator continuity at the plug but does this mean the accumulator solenoid actually opens when commanded to release its stored pressurized fluid? It's default is closed only opening when the vehicle is commanded to be raised. Gives a hand to pressurize the globes quickly that's all it's job is.

Maybe you could have an assistant press the up button while you listen (carefully) for a click and fluid moving at the end of the accumulator opposite the electrical plug that we tested continuity on yesterday.

see the diagram of the height accumulator on page 11 of the 20 page description @IndroCruise posted at post 105

A General Description of the Active Height Control (AHC) and Toyota Electronic Modulated Suspension (TEMS) systems and how they are meant to work. This 20-page description has good diagrams and explanations of each of the component parts of these systems. The hydraulic circuit diagrams are helpful when trying to visualize issues. This section is descriptive rather than diagnostic. It is worth printing for a careful read and later reference. This General Description is found easily at

https://lc100e.github.io/manual/

then follow the index tabs starting right at the top:
New Car Features > CHASSIS > Suspension > Active Height Control Suspension.

 

[LXKevin]

I'm also curious on the fluid color. Non-pink is trouble.

On the accumulator getting air in it, I don't think that should be a problem. The system should be able to bleed air in any part of it.

If you run the active test from techstream, can you keep the vehicle pumping while you crack open the accumulator breather? Logistically that might be a challenge, but I think that would be worthwhile. If the pump can be verified to run while the bleeder is open, you should have fluid coming out. If you can't get that to happen, it seems like there's a bad clog or the pump is worn dead.

Or the accumulator solenoid is not opening.

 

[aharlan001]

If the fluid was not pinkish, or pinkish getting dirty (grey, brown, nasty) when you first started bleeding, then the wrong fluid was in your system (read: not Mr. T AHC fluid).

Are you 1000000000% sure that there is no chance air got introduced into the system, either via running the resevoir dry or leaving a bleed valve cracked open without the AHC system running?

Couldn't find that thread but another thread said ahc fluid used to be yellow.

Per the Paddo method I used the truck is blead with the truck off with the vehicle in l... This was never a problem at the globes but maybe this was a problem at the height accumulator? I just read another thread that suggested that the height accumulator

If the fluid was not pinkish, or pinkish getting dirty (grey, brown, nasty) when you first started bleeding, then the wrong fluid was in your system (read: not Mr. T AHC fluid).

Are you 1000000000% sure that there is no chance air got introduced into the system, either via running the resevoir dry or leaving a bleed valve cracked open without the AHC system running?

I couldn't find that thread but another said ahc fluid used to be yellow so maybe my fluid was the correct type?

The method I used was to bleed in l with truck off. Didn't seem to be an issue at the globes as there was always flow but maybe a problem at the height accumulator? Also found another thread that suggested unless the rig goes into h then back to n the height accumulator won't be charged. Maybe this is why on subsequent bleeds the height accumulator was dry?Bleed AHC accumulator, but no fluid

 

[ramangain]

You can try this ... have the truck in L. With the rig running, crack open tube accumulator bleed valve and use a stick to press switch to raise to N (remember door needs to remain shut). If no fluid exits the tube accumulator but the truck tries to raise (ie globes are receiving fluid) then you should suspect either blockage from pump to tube accumulator or a bad valve directing fluid to tube accumulator.

We CAN and WILL narrow down to a single fault source.

 

[aharlan001]

Looking for clues


Remember the active test?
Yesterday at 12:21 PM post #40
Always happy to try something new. So with each test on lit up for about 1 second. With main relay, motor relay, front leveling solenoid, rear leveling solenoid I could actually hear something happening when it was activated. With accumulator solenoid, front gate solenoid, and rear gate solenoid I heard nothing... not sure what this means... ------------------------------GREAT QUESTION?

So we did test height accumulator continuity at the plug but does this mean the accumulator solenoid actually opens when commanded to release its stored pressurized fluid? It's default is closed only opening when the vehicle is commanded to be raised. Gives a hand to pressurize the globes quickly that's all it's job is.

Maybe you could have an assistant press the up button while you listen (carefully) for a click and fluid moving at the end of the accumulator opposite the electrical plug that we tested continuity on yesterday.

see the diagram of the height accumulator on page 11 of the 20 page description @IndroCruise posted at post 105

A General Description of the Active Height Control (AHC) and Toyota Electronic Modulated Suspension (TEMS) systems and how they are meant to work. This 20-page description has good diagrams and explanations of each of the component parts of these systems. The hydraulic circuit diagrams are helpful when trying to visualize issues. This section is descriptive rather than diagnostic. It is worth printing for a careful read and later reference. This General Description is found easily at

https://lc100e.github.io/manual/

then follow the index tabs starting right at the top:
New Car Features > CHASSIS > Suspension > Active Height Control Suspension.

Maybe I'm doing something wrong but in the active test section of techstream I can't keep any of those switches on. They can be triggered on but only for a second. I can trigger as I lay under there and listen.

 

[aharlan001]

You can try this ... have the truck in L. With the rig running, crack open tube accumulator bleed valve and use a stick to press switch to raise to N (remember door needs to remain shut). If no fluid exits the tube accumulator but the truck tries to raise (ie globes are receiving fluid) then you should suspect either blockage from pump to tube accumulator or a bad valve directing fluid to tube accumulator.

We CAN and WILL narrow down to a single fault source.

I can try this

 

[aharlan001]

Or the accumulator solenoid is not opening.

In the manual pump override sequence when you jump two pins, start truck, hit down 5+ times then up for 10 seconds you can force the pump to run but not in the active test section of ts. Even then I think it only runs for ten seconds. Getting the pump to run shouldn't be a problem. It will run if it is in l and the up button is hit. I can do this then open the height accumulator.