Unique AHC problem: no codes / no function (1 Viewer)

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I recently picked up a new to me 2002 LX470 at a very good price knowing that the AHC was non-functional. I have experience with the system, including using techstream to diagnose issues, but this one has me stumped.

Symptoms: The vehicle is at approximately the correct ride height, but quite stiff. No codes. Pressing either the up or down switch causes the green light to blink, but nothing happens. The light will blink forever until using the switch to move it back to N. No motor noise, no solenoid noise, nothing. All doors shut, confirmed with techstream. Comfort dial has no effect on ride.

Diagnostic work so far: Jumped the AHC motor directly, it seems to work. B+ and IG show 12V+. Used the techstream to perform active test on the relays, leveling solenoids, gate solenoids, etc. Nothing happens. No clicks, no noise, no movement. I performed the signal test, all signals are recognized by the ECU (steering, doors, low range, CDL, etc). Performed active test again using the jumper method, same result as before (no movement, no noises, nothing).

I unplugged the harness to the control valve and immediately had codes. That tells me the ECU isn't totally dead. It seems to receive signals just fine, but isn't outputting anything. I have also checked the main relay and the AHC relay, and associated fuses. The main relay is powered and works. The AHC relay tests fine, but never receives any signal to activate.

Height sensors also check out fine, I have tested them throughout their range and have found no dead spots (using the techstream)
Pressure sensors read zero (accumulator, and all 4 corners). I can't go through the proper process (low to N) to check them.

I'm fairly stumped, and thinking about pulling the trigger on a used AHC computer.
 
I have also checked the main relay and the AHC relay, and associated fuses. The main relay is powered and works. The AHC relay tests fine, but never receives any signal to activate.

Great description of test work and outcomes in pursuit of diagnosis -- much appreciated -- makes it much easier for the reader to follow!!

First, to avoid confusion in remote diagnosis from one side of the world to the other, just wanting to make sure that we are on the same page with item names -- not sure what is being described in the Post #1 as the "main relay".

As I understand the FSM labels,
  • the "AHC Relay" is the one in the Junction Box in the Engine Compartment and the 50 Amp AHC fuse is nearby in the same Junction Box (layouts vary slightly with different models and years) -- broken fuse or fault in this relay means no power to the motor at AHC Pump, and,
  • the "AHC Main Relay" is the one attached to the AHC ECU under the dashboard and the relevant fuses are the AHC-IG fuse and the AHC-B fuse -- these fuses are located in the Junction Box behind the Left Hand Cowl (next to the driver's left foot in your case, panel layouts vary slightly with different models and years) -- non-operation of the AHC Main Relay means non-operation of any part of the AHC and TEMS systems, neither under automatic ECU control nor under "Active Test".
So I am taking it that
  • AHC Relay and AHC Pump (Motor) operation is healthy with no reason at this stage to suspect a pump partial blockage within its internal strainers (this usually would throw one or several DTC's), and,
  • the AHC-IG fuse and the AHC-B fuse are OK and the "AHC Main Relay" (mounted on the AHC ECU) "tests fine, but never receives any signal to activate".
Hoping I have understood this correctly. If so, non-operation of the AHC Main Relay means that there is no power to the AHC and TEMS systems which in turn means there is no AHC or TEMS functionality and also means that "active test" cannot work.

If the relevant fuses and AHC Main Relay are healthy, then the conclusion would be that one or other of the eight or so FSM-defined 'fail safe functions' are operating -- all having similar prohibitions (although not exactly the same) on AHC and TEMS functions.

As the FSM indicates, faults leading to 'fail safe functions' can and do occur without presentation of a Diagnostic Trouble Code (DTC) -- this can occur when there is a Sensor circuit fault somewhere but it does not breach the DTC 'rules' for that particular Sensor Circuit. The Height Control Sensor circuits (Sensor + Connector + Harness) are most common and famous in this regard -- presence of a Height Control Sensor DTC certainly indicates a fault BUT absence of a DTC does not provide assurance the Height Control Sensor circuit is healthy and functioning correctly. Sensor removal and testing per FSM or some equivalent procedure independent of Techstream is necessary. A non-FSM method identified by @PADDO and @uHu and others is possible -- involves testing for a smooth and correct change in Sensor resistance (ohms) through its swing -- see Post #2 in this thread:

Testing a Height Control Sensor circuit using Techstream involves several assumptions and may not be reliable.

The Pressure Sensor attached to the AHC Pump is not mentioned in your list. Failure is unusual but for avoidance of doubt it would be worthwhile to check this Sensor using the FSM procedure -- it cannot be tested on Techstream. This is the only Pressure Sensor in the LC100/LX470 AHC/TEMS systems -- it measures the final Front AHC, Rear AHC and Height Control Accumulator pressures sequentially using the N > LO > N procedure you have described (plus allowing time to recharge the Height Control Accumulator at the end of a raise).

When all else fails and in the absence of better ideas from other IH8MUD Members, then the suggestion would be
  • review the FSM "Problems Symptoms Table" one more time, and then,
  • expose the AHC ECU connectors (without disengaging the plugs) and test for the voltages listed in "Terminals of ECU" table.
The purpose here is to discover the problematic circuit, then backtrack/search for possible circuit breaks in the wiring harness and or damaged connectors causing errant signals or lack of signals to the AHC ECU

It would seem worthwhile to do these checks before going to the trouble of trialling a replacement ECU.

If an FSM is not readily available, the following reference may be helpful. It is the LC100 version but is equally applicable to LX470 on AHC/TEMS matters:

At LHS index panel at the opening page, scroll to
+ Repair Manual
+ DIAGNOSTICS
+ ACTIVE HEIGHT CONTROL & SKYHOOK TEMS
 

Attachments

  • AHC problem symptom table.pdf
    69 KB · Views: 94
  • AHC - Terminals of ECU.pdf
    58.4 KB · Views: 61
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I had the same problem one time. It ended up being a broken wire in the harness in the tailgate. It thought the door was open and wouldn't work.
 
I had the same problem one time. It ended up being a broken wire in the harness in the tailgate. It thought the door was open and wouldn't work.

Good call -- good reminder that there are some 'lockout conditions' like this that prevent AHC operation -- and because it seems 'normal' to AHC ECU (circuit fault looks the same as 'door open'), there is no DTC.

Suspect similar fault in brake light circuit might have similar effect if it indicates to ECU that 'foot-brake is on'. There may be others elsewhere in IG circuit. If the effect prevents power arriving at the AHC Main Relay -- then no AHC/TEMS operation.

This made me remember a series of Posts in the thread linked below where @suprarx7nut sleuthed his way to a solution to a similar problem. There are good explanations and illustrations at Post #13 through Post #17 here:

 
Last edited:
I had the same problem one time. It ended up being a broken wire in the harness in the tailgate. It thought the door was open and wouldn't work.
OP mentioned techstream is showing all doors as closed. I do wonder about a faulty brake or e-brake signal as others have mentioned.

Screenshots of the techstream screen with all the AHC data may be useful for us to review.
 
Any resolution to this? I am having a similar issue...
 
Any resolution to this? I am having a similar issue...

If @mulecity is still on this Forum, it would be good to know about any outcome -- successful or unsuccessful?

@TEXAS 57 -- good if you could tell us your story and provide a Techstream screenshot?
 
If @mulecity is still on this Forum, it would be good to know about any outcome -- successful or unsuccessful?

@TEXAS 57 -- good if you could tell us your story and provide a Techstream screenshot?

Thanks. Sorry for the delay. It took me a while to get back out there.

Worked perfect for years. 1999 LX470
Huge rainstorm, No high water driving but water poured in from the sunroof drains (I assume haven't dug into it yet; sunroof doesn't work but bought all the replacement parts). Water came in on my left foot from under the dash (LHD). No issues, turned the car off, after the rain cleaned up.

Next morning, go out to air out the car, turn it on to drive it up in the driveway and AHC OFF light is flashing and the suspension is stuck in sport mode (where I left it when I parked). Up and Down just blinks but never happens and no suspension settings adjustments. Stuck on normal height.

Thinking something got wet and shorted, I checked the kick panel AHC IG Fuse and AHC -B fuse. Both were fine, checked with meter and switched out. (just in case).

Hooked Techstream up - +B is low. Sensors seem all over the place but pressures were reading good about 6 months ago. I did replace the rear trailing arms a month or so ago and did have to fiddle with the rear height sensor. No issues since then.
1663355409260.png

When I try to run Active tests, i can hear the little can relay activating every test has this error: (Doors closed, foot off brake)
1663355669972.png

+B reading goes up after relay triggered and then slowly goes back down and that's where I am at.
1663355760662.png
 
Thanks. Sorry for the delay. It took me a while to get back out there.

Worked perfect for years. 1999 LX470
Huge rainstorm, No high water driving but water poured in from the sunroof drains (I assume haven't dug into it yet; sunroof doesn't work but bought all the replacement parts). Water came in on my left foot from under the dash (LHD). No issues, turned the car off, after the rain cleaned up.

Next morning, go out to air out the car, turn it on to drive it up in the driveway and AHC OFF light is flashing and the suspension is stuck in sport mode (where I left it when I parked). Up and Down just blinks but never happens and no suspension settings adjustments. Stuck on normal height.

Thinking something got wet and shorted, I checked the kick panel AHC IG Fuse and AHC -B fuse. Both were fine, checked with meter and switched out. (just in case).

Hooked Techstream up - +B is low. Sensors seem all over the place but pressures were reading good about 6 months ago. I did replace the rear trailing arms a month or so ago and did have to fiddle with the rear height sensor. No issues since then. View attachment 3116600
When I try to run Active tests, i can hear the little can relay activating every test has this error: (Doors closed, foot off brake)
View attachment 3116604
+B reading goes up after relay triggered and then slowly goes back down and that's where I am at.
View attachment 3116606

The power circuit voltages look strange in the Techstream read-outs -- "IG" means the circuit which is operating when the Ignition is switched ON, +B means the bus line -- battery voltage less any losses between battery and the Suspension Electronic Control Unit (ECU). Are there any other 'strange' electrical signals or lights on the dashboard? A combination of heavy rain with degraded windscreen seals or degraded sunroof drains can result in moisture in the Junction Boxes behind the kickpanels forward of the Front doors causing strange effects -- if this has happened, suggest remove covers and allow these areas to dry out (with the battery disconnected).

For good order, suggest check battery including connections at battery posts and Ground connection to body and engine in the usual way, ditto alternator function and voltages -- all just to make sure that power supply to AHC is available. Voltage decay at +B does arouse suspicions.

Looking at the Techstream screenshots -- easy items like "Door Switch -- OFF" and "Stop Light Switch -- OFF" are good. "Steering Angle" at -2.25 degrees is fine.

The "Motor Relay -- OFF" refers to the AHC Motor Relay in the Junction Box in the Engine Bay -- "OFF" is normal unless the motor for the AHC Pump actually is operating.

"Oil Temperature Sensor -- 154degF" means AHC Fluid temperature is quite hot -- and means that the AHC Pump has been trying to do something, so question-mark about what is going on with hot pump but no AHC movement -- possibility of partial blockage at the tiny strainers within the AHC Pump?? If the AHC Pump is starved of fluid, or, trying to build excessive pressure against a blockage, then the relevant 'fail safe function' will operate to protect the AHC Pump each time the AHC Pump attempts to operate -- the AHC system will cease operation, the AHC green OFF light will flash, and the ECU will adopt the FSM-specified 'fail safe' settings, and also record the relevant DTC(s).

The indication "Main Relay Expectation - OFF" also looks suspicious in the first screenshot -- was it ON or OFF in the second screenshot? (The information is chopped off in the image shown -- please don't do this). This refers to the AHC Main Relay which either piggy-backs onto the ECU located under the dash or is nearby (may vary with model year). Usually this would show "ON" meaning "ready to operate". If the AHC Main Relay is faulty or non-functional, the AHC system will not operate at all, including under "Active Test" -- and in this case the ECU will set the TEMS system to "Sports Mode" and record the relevant DTC.

Five Diagnostic Trouble Codes (DTC's) are shown in both screenshots. Suggest cancel these either using Techstream or manually -- that eliminates any history lingering in the ECU memory. Then the presently existing DTC's will re-establish themselves immediately on start-up and/or attempts to operate the AHC system and can be reviewed without any historical confusion. Suggest use Techstream to identify the actual DTC code numbers -- Techstream also may give a brief indication of the cause but best to look up the code number and the full explanations in the "DIAGNOSTICS" section in the FSM (reference below if needed).

Some faults indicated by DTC's also may be associated with a 'fail safe function'. There are around eight of these 'fail safe functions' defined in the FSM for various different fault conditions -- all with similar protective effects prohibiting Active Height Control (AHC) function and prohibiting adaptive damping by the Toyota Electronic Modulated Suspension (TEMS).

Also suggest be aware that the DIAGNOSTIC system has limitations. For example, the presence of any of the Height Control Sensor DTC's indicates a definite fault -- but the reverse is not true. Absence of any Height Control Sensor DTC's DOES NOT provide assurance that the Height Control Sensors are healthy. This is described in various other posts on IH8MUD -- for example Post #76 here:

Impex is LEGIT 4 new AHC globes. Door To Door from Japan, less than 2 weeks - https://forum.ih8mud.com/threads/impex-is-legit-4-new-ahc-globes-door-to-door-from-japan-less-than-2-weeks.1256544/page-4#post-14001281

And at Post #15 here:

Intro and yet another AHC thread… - https://forum.ih8mud.com/threads/intro-and-yet-another-ahc-thread.1281317/#post-14403443

And with more pictures at Post #932 here:

Definitive list of AHC maintenance items - https://forum.ih8mud.com/threads/definitive-list-of-ahc-maintenance-items.604577/page-47#post-14378858

Unless there is some cause of 'lean' of the vehicle, or unless the Sensors require adjustment, or unless there is one or more faulty Sensors, then the readings on your screenshots should be close to zero with differences within +/- 0.2 inch or +/- 5 mm.

Given the symptoms and their on-set after wet weather (moisture ingress?) and if the Height Control Sensors are original, then these 23 years old 'wear items' are not above suspicion. The difference between the FL and FR Sensor readings does raise an eyebrow -- especially if the readings were taken correctly, meaning with the vehicle on a level surface (such as a concrete garage/workshop floor, not a sloping driveway nor in the street), no persons or temporary loads on board, fuel full, steering straight ahead, and after Front 'cross-level' has been checked and corrected if necessary.

Suggest that it is always important to consider the DTC's and the actual vehicle behaviour together when making a diagnosis and not regard Techstream as an all-seeing black box. Techstream or other AHC-compatible scanner certainly is is an essential tool for work on the AHC/TEMS systems -- along with a multimeter -- but human observation and judgement is needed as well.

Suggested next steps -- check electrical system, identify the current DTC's and compare with observed vehicle symptoms.

Reference:
LC100 Workshop Manual - https://lc100e.github.io/ then follow the tabs at the index panel on LHS of opening page
+ Repair Manual
+ DIAGNOSTICS
+ Active Height Control & Skyhook TEMS
 
Last edited:
The power circuit voltages look strange in the Techstream read-outs -- "IG" means the circuit which is operating when the Ignition is switched ON, +B means the bus line -- battery voltage less any losses between battery and the Suspension Electronic Control Unit (ECU). Are there any other 'strange' electrical signals or lights on the dashboard? A combination of heavy rain with degraded windscreen seals or degraded sunroof drains can result in moisture in the Junction Boxes behind the kickpanels forward of the Front doors causing strange effects -- if this has happened, suggest remove covers and allow these areas to dry out (with the battery disconnected).

For good order, suggest check battery including connections at battery posts and Ground connection to body and engine in the usual way, ditto alternator function and voltages -- all just to make sure that power supply to AHC is available. Voltage decay at +B does arouse suspicions.

Looking at the Techstream screenshots -- easy items like "Door Switch -- OFF" and "Stop Light Switch -- OFF" are good. "Steering Angle" at -2.25 degrees is fine.

The "Motor Relay -- OFF" refers to the AHC Motor Relay in the Junction Box in the Engine Bay -- "OFF" is normal unless the motor for the AHC Pump actually is operating.

"Oil Temperature Sensor -- 154degF" means AHC Fluid temperature is quite hot -- and means that the AHC Pump has been trying to do something, so question-mark about what is going on with hot pump but no AHC movement -- possibility of partial blockage at the tiny strainers within the AHC Pump?? If the AHC Pump is starved of fluid, or, trying to build excessive pressure against a blockage, then the relevant 'fail safe function' will operate to protect the AHC Pump each time the AHC Pump attempts to operate -- the AHC system will cease operation, the AHC green OFF light will flash, and the ECU will adopt the FSM-specified 'fail safe' settings, and also record the relevant DTC(s).

The indication "Main Relay Expectation - OFF" also looks suspicious in the first screenshot -- was it ON or OFF in the second screenshot? (The information is chopped off in the image shown -- please don't do this). This refers to the AHC Main Relay which either piggy-backs onto the ECU located under the dash or is nearby (may vary with model year). Usually this would show "ON" meaning "ready to operate". If the AHC Main Relay is faulty or non-functional, the AHC system will not operate at all, including under "Active Test" -- and in this case the ECU will set the TEMS system to "Sports Mode" and record the relevant DTC.

Five Diagnostic Trouble Codes (DTC's) are shown in both screenshots. Suggest cancel these either using Techstream or manually -- that eliminates any history lingering in the ECU memory. Then the presently existing DTC's will re-establish themselves immediately on start-up and/or attempts to operate the AHC system and can be reviewed without any historical confusion. Suggest use Techstream to identify the actual DTC code numbers -- Techstream also may give a brief indication of the cause but best to look up the code number and the full explanations in the "DIAGNOSTICS" section in the FSM (reference below if needed).

Some faults indicated by DTC's also may be associated with a 'fail safe function'. There are around eight of these 'fail safe functions' defined in the FSM for various different fault conditions -- all with similar protective effects prohibiting Active Height Control (AHC) function and prohibiting adaptive damping by the Toyota Electronic Modulated Suspension (TEMS).

Also suggest be aware that the DIAGNOSTIC system has limitations. For example, the presence of any of the Height Control Sensor DTC's indicates a definite fault -- but the reverse is not true. Absence of any Height Control Sensor DTC's DOES NOT provide assurance that the Height Control Sensors are healthy. This is described in various other posts on IH8MUD -- for example Post #76 here:

Impex is LEGIT 4 new AHC globes. Door To Door from Japan, less than 2 weeks - https://forum.ih8mud.com/threads/impex-is-legit-4-new-ahc-globes-door-to-door-from-japan-less-than-2-weeks.1256544/page-4#post-14001281

And at Post #15 here:

Intro and yet another AHC thread… - https://forum.ih8mud.com/threads/intro-and-yet-another-ahc-thread.1281317/#post-14403443

And with more pictures at Post #932 here:

Definitive list of AHC maintenance items - https://forum.ih8mud.com/threads/definitive-list-of-ahc-maintenance-items.604577/page-47#post-14378858

Unless there is some cause of 'lean' of the vehicle, or unless the Sensors require adjustment, or unless there is one or more faulty Sensors, then the readings on your screenshots should be close to zero with differences within +/- 0.2 inch or +/- 5 mm.

Given the symptoms and their on-set after wet weather (moisture ingress?) and if the Height Control Sensors are original, then these 23 years old 'wear items' are not above suspicion. The difference between the FL and FR Sensor readings does raise an eyebrow -- especially if the readings were taken correctly, meaning with the vehicle on a level surface (such as a concrete garage/workshop floor, not a sloping driveway nor in the street), no persons or temporary loads on board, fuel full, steering straight ahead, and after Front 'cross-level' has been checked and corrected if necessary.

Suggest that it is always important to consider the DTC's and the actual vehicle behaviour together when making a diagnosis and not regard Techstream as an all-seeing black box. Techstream or other AHC-compatible scanner certainly is is an essential tool for work on the AHC/TEMS systems -- along with a multimeter -- but human observation and judgement is needed as well.

Suggested next steps -- check electrical system, identify the current DTC's and compare with observed vehicle symptoms.

Reference:
LC100 Workshop Manual - https://lc100e.github.io/ then follow the tabs at the index panel on LHS of opening page
+ Repair Manual
+ DIAGNOSTICS
+ Active Height Control & Skyhook TEMS
Thanks for replying. Forgive the length of time that has passed as have limited time to work.

I may be wrong, but I feel the 155*F temp is normal as it has been near 100*F here in Houston, TX and most everything under the hood is the same temp or warmer with a temp gun. The car was sitting and idling for a long time in the sun as well.

I have taken voltage readings from all over the vehicle and see very little to no voltage drops throughout the vehicle. I also undid almost every ground about 2 years ago, cleaned and dielectric greased them while chasing a headlight issue that has been resolved.

I have unplugged the alternator, checked connection and plugged back in.

I have disconnected the battery for an hour and plugged it back in. The battery is less than 6 months old and has new factory terminals.

With Techstream, I can get the reading that there are the 5 diagnostic codes but I cannot read them. I get the error message above when I try to access. I can erase them and they come back , but still cannot see them.
 
The power circuit voltages look strange in the Techstream read-outs -- "IG" means the circuit which is operating when the Ignition is switched ON, +B means the bus line -- battery voltage less any losses between battery and the Suspension Electronic Control Unit (ECU). Are there any other 'strange' electrical signals or lights on the dashboard? A combination of heavy rain with degraded windscreen seals or degraded sunroof drains can result in moisture in the Junction Boxes behind the kickpanels forward of the Front doors causing strange effects -- if this has happened, suggest remove covers and allow these areas to dry out (with the battery disconnected).

For good order, suggest check battery including connections at battery posts and Ground connection to body and engine in the usual way, ditto alternator function and voltages -- all just to make sure that power supply to AHC is available. Voltage decay at +B does arouse suspicions.

Looking at the Techstream screenshots -- easy items like "Door Switch -- OFF" and "Stop Light Switch -- OFF" are good. "Steering Angle" at -2.25 degrees is fine.

The "Motor Relay -- OFF" refers to the AHC Motor Relay in the Junction Box in the Engine Bay -- "OFF" is normal unless the motor for the AHC Pump actually is operating.

"Oil Temperature Sensor -- 154degF" means AHC Fluid temperature is quite hot -- and means that the AHC Pump has been trying to do something, so question-mark about what is going on with hot pump but no AHC movement -- possibility of partial blockage at the tiny strainers within the AHC Pump?? If the AHC Pump is starved of fluid, or, trying to build excessive pressure against a blockage, then the relevant 'fail safe function' will operate to protect the AHC Pump each time the AHC Pump attempts to operate -- the AHC system will cease operation, the AHC green OFF light will flash, and the ECU will adopt the FSM-specified 'fail safe' settings, and also record the relevant DTC(s).

The indication "Main Relay Expectation - OFF" also looks suspicious in the first screenshot -- was it ON or OFF in the second screenshot? (The information is chopped off in the image shown -- please don't do this). This refers to the AHC Main Relay which either piggy-backs onto the ECU located under the dash or is nearby (may vary with model year). Usually this would show "ON" meaning "ready to operate". If the AHC Main Relay is faulty or non-functional, the AHC system will not operate at all, including under "Active Test" -- and in this case the ECU will set the TEMS system to "Sports Mode" and record the relevant DTC.

Five Diagnostic Trouble Codes (DTC's) are shown in both screenshots. Suggest cancel these either using Techstream or manually -- that eliminates any history lingering in the ECU memory. Then the presently existing DTC's will re-establish themselves immediately on start-up and/or attempts to operate the AHC system and can be reviewed without any historical confusion. Suggest use Techstream to identify the actual DTC code numbers -- Techstream also may give a brief indication of the cause but best to look up the code number and the full explanations in the "DIAGNOSTICS" section in the FSM (reference below if needed).

Some faults indicated by DTC's also may be associated with a 'fail safe function'. There are around eight of these 'fail safe functions' defined in the FSM for various different fault conditions -- all with similar protective effects prohibiting Active Height Control (AHC) function and prohibiting adaptive damping by the Toyota Electronic Modulated Suspension (TEMS).

Also suggest be aware that the DIAGNOSTIC system has limitations. For example, the presence of any of the Height Control Sensor DTC's indicates a definite fault -- but the reverse is not true. Absence of any Height Control Sensor DTC's DOES NOT provide assurance that the Height Control Sensors are healthy. This is described in various other posts on IH8MUD -- for example Post #76 here:

Impex is LEGIT 4 new AHC globes. Door To Door from Japan, less than 2 weeks - https://forum.ih8mud.com/threads/impex-is-legit-4-new-ahc-globes-door-to-door-from-japan-less-than-2-weeks.1256544/page-4#post-14001281

And at Post #15 here:

Intro and yet another AHC thread… - https://forum.ih8mud.com/threads/intro-and-yet-another-ahc-thread.1281317/#post-14403443

And with more pictures at Post #932 here:

Definitive list of AHC maintenance items - https://forum.ih8mud.com/threads/definitive-list-of-ahc-maintenance-items.604577/page-47#post-14378858

Unless there is some cause of 'lean' of the vehicle, or unless the Sensors require adjustment, or unless there is one or more faulty Sensors, then the readings on your screenshots should be close to zero with differences within +/- 0.2 inch or +/- 5 mm.

Given the symptoms and their on-set after wet weather (moisture ingress?) and if the Height Control Sensors are original, then these 23 years old 'wear items' are not above suspicion. The difference between the FL and FR Sensor readings does raise an eyebrow -- especially if the readings were taken correctly, meaning with the vehicle on a level surface (such as a concrete garage/workshop floor, not a sloping driveway nor in the street), no persons or temporary loads on board, fuel full, steering straight ahead, and after Front 'cross-level' has been checked and corrected if necessary.

Suggest that it is always important to consider the DTC's and the actual vehicle behaviour together when making a diagnosis and not regard Techstream as an all-seeing black box. Techstream or other AHC-compatible scanner certainly is is an essential tool for work on the AHC/TEMS systems -- along with a multimeter -- but human observation and judgement is needed as well.

Suggested next steps -- check electrical system, identify the current DTC's and compare with observed vehicle symptoms.

Reference:
LC100 Workshop Manual - https://lc100e.github.io/ then follow the tabs at the index panel on LHS of opening page
+ Repair Manual
+ DIAGNOSTICS
+ Active Height Control & Sk
 

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