LX470 - Front Left Suspension Damper Stuck at Maximum Stiffness (1 Viewer)

[japansam23]

TL;DR - I believe my front left suspension damper is stuck at the stiffest setting, causing bad ride quality.

This is my first post here, and I'm only posting because I think I've read every AHC thread there is. I have a 2000 LX470 with 145,000 miles, and I'm trying to troubleshoot terrible ride quality. I have the same symptoms that many others have described, I can hear and feel every tiny bump or crack in the road, even on seemingly smooth asphalt, regardless of the variable suspension switch setting. I have no complaints about the ride quality on the highway.

Most recently, I performed the 16 step damper check for the first time, and all positions EXCEPT the front left properly increased in stiffness at each step. At the start of the test, Techstream indicated that the front and rear were both at step 1, but the front left felt like it was at maximum stiffness, requiring my full body weight to cause movement, while all other corners had significant soft bounce. I pulled all AHC marked fuses, and disconnected the negative battery terminal for good measure, in an effort to clear any faults or error states that Techstream wasn't showing me. I performed the test again 2 hours later with the same results.

Here are actions I have done so far, in the order that I did them, just to provide a record of my troubleshooting process:

1. - Corrected high AHC pressures via torsion bar adjustment, and 30mm spacers
2. - Verified proper vehicle height and cross-leveling via FSM procedures
3. - New sway bar and end link bushings, front and rear
4. - Fluid flush via @PADDO 's 1 can easy flush method (fluid was dark, but had minimal bubbles/frothing)
5. - 16 step damper response check via FSM procedure

Here are some known facts:

1. - The variable suspension switch functions properly and I can feel differences at each position
2. - In Techstream, with the vehicle idling on flat ground, my front and rear pressures are within FSM spec
3. - Techstream shows the damper steps, front and rear, at 8 while idling on flat ground
4. - I get 10 graduation marks on the AHC reservoir when going from LOW to NEUTRAL
5. - Techstream shows no AHC trouble codes
6. - During the 16 step damper test, all positions EXCEPT the front left properly increase in damping resistance (front left is very stiff, comparable to step 16)
7. - AHC operates properly, lowering and raising the truck with no issues

It seems clear that my next step is to get under the truck and start looking for physical damge to wiring or connectors and then break out the multimeter. I have read a few threads about exhaust leaks melting connectors, but I'm puzzled because in those cases they had AHC touble codes visible in Techstream. My front left header did have a slight leak before I went to new Doug Thorley headers, so that leak could have damaged something. I do not believe the new headers damaged anything, because the ride was bad before I installed them. Let me know what you guys think and feel free to drop insight that you have. Also let me know if there's any info I'm missing that could be helpful in diagnosing. I'm gonna be reading my FSM's, trying to find where to start looking and probing.

 

[caslim]

Mine acts up like this as well sometimes. Not sure if the globes are just getting old. Everything is within spec as well.

 

[ramangain]

Great job diagnosing thusfar, congrats.

Like you, I do believe it is time to take some measurements with a DMM at the FL damper and the next connector upstream.

 

[IndroCruise]

Reported "Corrective actions" 1 to 5 are noted and therefore can assume that tests have been done on level surface, steering straight ahead, vehicle at standard weight (fuel full, no freight nor persons on board), cross-levelled and with operating heights front and rear per IH8MUD recommendations, and front and rear AHC pressures within FSM-specified ranges for HI/LO Test.

Reported "Known facts" 1 to 7 are noted and respected.

Using information and the AHC Diagnostic section of the FSM attached to a previous post at this link and also this prior post, suggest continue your diagnosis in the following way:

• physically inspect underbody, check for corrosion or other damage to electrical harness and connectors and mechanical linkages at all Height Control Sensors (two in front, one at rear), and also, electrical harness and connectors at the Damping Force Control Actuators (to which the Gas Chambers a.k.a. ‘globes’ are attached),
• be aware that while HI/LO Test = 10 graduations at AHC Tank suggests that ‘globes’ are OK, it is possible (but unusual) that only the Left Front ‘globe’ has failed. Other ‘globes’ may be good enough to displace sufficient fluid to to give a healthy test result. HI/LO Test cannot detect condition of an individual ‘globe’ but only indicates the condition of all four ‘globes’ overall. However, it seems unlikely that just one ‘globe’ would ‘wear out’ at a different rate to the others if all are undamaged, same age, and were installed at the same time. It also seems unlikely that the other ‘globes’ would be good enough to compensate sufficiently to give 10 graduations if one ‘globe’ has completely failed (lost all nitrogen). AHC pressure readings tell NOTHING about the internal condition of ‘globes’,
• For the moment, assume ‘globes’ are OK,
• Also be aware that, irrespective of internal ‘globe’ condition, many ‘fail-safe’ modes occur under various fault conditions in the Active Height Control and Toyota Electronic Modulated Suspension (AHC/TEMS) systems. These conditions and effects are specified in the FSM section at the link given above – two examples come to mind with the following symptoms -- quoting from the FSM in italics:
  • HEIGHT CONTROL SENSOR CIRCUIT
    Note description of “Fail safe function”:
    “If a trouble occurs in the height control sensor circuit, the height control is prohibited after the ECU has adjusted the vehicle height to the standard (fluid pressure correspond to the standard height)”.
  • In this condition, you will not get a smooth ride, especially noticeable at low speed – damping will stay at Step 8 (Note: 8 is the proper position when the vehicle is not moving, unless the 16 Step Test procedure is being applied),
  • Noted that you are observing 16 but it is hard to ignore the risk of Height Control Sensor malfunction given the environment in which these sensors live, and in any case inspection and testing is not difficult and deals with this possibility,
  • Suggest do the 16 Step test manually with connection made at DLC1 (E1 to Ts) per FSM to eliminate any possibility of false signals,
  • DAMPING FORCE CONTROL ACTUATOR CIRCUIT
  • This section of the FSM describes a range of fault conditions in this circuit (at each such actuator). “The AHC Electronic Control Unit (ECU) sends a signal to damping force control actuator to drive the rotary valve of the shock absorber changing the shock absorber damping force. The actuator is driven electromagnetically by step motor so that it can accurately follow the driving conditions that change frequently”.
  • Note the description of the “Fail-safe function”
  • “If trouble occurs in the front or rear wheel damping force control actuator circuit, ECU prohibits the damping force control after the ECU has returned the damping force of the other side wheel to the normal condition”.
  • In this condition you will not get a smooth ride.
• As the 16 Step Test places suspicion on Left Front suspension, and even though no Diagnostic Trouble Codes (DTC’s) are reported, consider possible faults and 'fail-safe' effects caused by
  • Front Left Height Control Sensor – a common problem,
  • Front Left Height Damping Force Control Actuator – a less common problem,
• Remove and inspect Front Left Height Control Sensor (first mark and photograph position of adjusters) – removal is straight forward – two bolts at bracket on chassis, one connecting bolt on linkage, two cable clips on cable rising to engine bay, then follow cable to the connector in engine bay above and disconnect,
• Test Front Left Height Control Sensor as described in FSM or as described by uHu in a link within the post mentioned far above,
• Test voltage provided at the now unplugged connector in the engine bay,
• Carefully remove cover from the actual Sensor and inspect internal condition of carbon tracks, tiny brushes and spring connectors and their seats, clean up as required, re-test, decide whether to re-install the existing sensor, or, replace with a new Sensor. (Note: The performance of the AHC/TEMS systems and the readouts by Techstream are only as good as the signals provided to the Electronic Control Unit (ECU) by the various Sensors. If in doubt about the condition of old Sensors, replace them),
• Test drive vehicle with refurbished or replacement Height Control Sensor installed,
• If problem continues, disconnect the connector at the Front Left Damping Force Control Actuator and test resistances as described in the AHC Diagnostics section of the FSM as attached within the link far above,
• If problems continue, work through the PROBLEM SYMPTOMS TABLE given in the AHC Diagnostics section of the FSM, also as given at the link far above,

Hope this helps!

 

[japansam23]

Reported "Corrective actions" 1 to 5 are noted and therefore can assume that tests have been done on level surface, steering straight ahead, vehicle at standard weight (fuel full, no freight nor persons on board), cross-levelled and with operating heights front and rear per IH8MUD recommendations, and front and rear AHC pressures within FSM-specified ranges for HI/LO Test.

Reported "Known facts" 1 to 7 are noted and respected.

Using information and the AHC Diagnostic section of the FSM attached to a previous post at this link and also this prior post, suggest continue your diagnosis in the following way:

• physically inspect underbody, check for corrosion or other damage to electrical harness and connectors and mechanical linkages at all Height Control Sensors (two in front, one at rear), and also, electrical harness and connectors at the Damping Force Control Actuators (to which the Gas Chambers a.k.a. ‘globes’ are attached),
• be aware that while HI/LO Test = 10 graduations at AHC Tank suggests that ‘globes’ are OK, it is possible (but unusual) that only the Left Front ‘globe’ has failed. Other ‘globes’ may be good enough to displace sufficient fluid to to give a healthy test result. HI/LO Test cannot detect condition of an individual ‘globe’ but only indicates the condition of all four ‘globes’ overall. However, it seems unlikely that just one ‘globe’ would ‘wear out’ at a different rate to the others if all are undamaged, same age, and were installed at the same time. It also seems unlikely that the other ‘globes’ would be good enough to compensate sufficiently to give 10 graduations if one ‘globe’ has completely failed (lost all nitrogen). AHC pressure readings tell NOTHING about the internal condition of ‘globes’,
• For the moment, assume ‘globes’ are OK,
• Also be aware that, irrespective of internal ‘globe’ condition, many ‘fail-safe’ modes occur under various fault conditions in the Active Height Control and Toyota Electronic Modulated Suspension (AHC/TEMS) systems. These conditions and effects are specified in the FSM section at the link given above – two examples come to mind with the following symptoms -- quoting from the FSM in italics:
  • HEIGHT CONTROL SENSOR CIRCUIT
    Note description of “Fail safe function”:
    “If a trouble occurs in the height control sensor circuit, the height control is prohibited after the ECU has adjusted the vehicle height to the standard (fluid pressure correspond to the standard height)”.
  • In this condition, you will not get a smooth ride, especially noticeable at low speed – damping will stay at Step 8 (Note: 8 is the proper position when the vehicle is not moving, unless the 16 Step Test procedure is being applied),
  • Noted that you are observing 16 but it is hard to ignore the risk of Height Control Sensor malfunction given the environment in which these sensors live, and in any case inspection and testing is not difficult and deals with this possibility,
  • Suggest do the 16 Step test manually with connection made at DLC1 (E1 to Ts) per FSM to eliminate any possibility of false signals,
  • DAMPING FORCE CONTROL ACTUATOR CIRCUIT
  • This section of the FSM describes a range of fault conditions in this circuit (at each such actuator). “The AHC Electronic Control Unit (ECU) sends a signal to damping force control actuator to drive the rotary valve of the shock absorber changing the shock absorber damping force. The actuator is driven electromagnetically by step motor so that it can accurately follow the driving conditions that change frequently”.
  • Note the description of the “Fail-safe function”
  • “If trouble occurs in the front or rear wheel damping force control actuator circuit, ECU prohibits the damping force control after the ECU has returned the damping force of the other side wheel to the normal condition”.
  • In this condition you will not get a smooth ride.
• As the 16 Step Test places suspicion on Left Front suspension, and even though no Diagnostic Trouble Codes (DTC’s) are reported, consider possible faults and 'fail-safe' effects caused by
  • Front Left Height Control Sensor – a common problem,
  • Front Left Height Damping Force Control Actuator – a less common problem,
• Remove and inspect Front Left Height Control Sensor (first mark and photograph position of adjusters) – removal is straight forward – two bolts at bracket on chassis, one connecting bolt on linkage, two cable clips on cable rising to engine bay, then follow cable to the connector in engine bay above and disconnect,
• Test Front Left Height Control Sensor as described in FSM or as described by uHu in a link within the post mentioned far above,
• Test voltage provided at the now unplugged connector in the engine bay,
• Carefully remove cover from the actual Sensor and inspect internal condition of carbon tracks, tiny brushes and spring connectors and their seats, clean up as required, re-test, decide whether to re-install the existing sensor, or, replace with a new Sensor. (Note: The performance of the AHC/TEMS systems and the readouts by Techstream are only as good as the signals provided to the Electronic Control Unit (ECU) by the various Sensors. If in doubt about the condition of old Sensors, replace them),
• Test drive vehicle with refurbished or replacement Height Control Sensor installed,
• If problem continues, disconnect the connector at the Front Left Damping Force Control Actuator and test resistances as described in the AHC Diagnostics section of the FSM as attached within the link far above,
• If problems continue, work through the PROBLEM SYMPTOMS TABLE given in the AHC Diagnostics section of the FSM, also as given at the link far above,

Hope this helps!

Awesome breakdown, thanks for taking the time to write that out. It's interesting that you note 1 globe could go bad, I also was having that thought. I've considered removing the front 2 globes, inspecting them, and swapping them to opposite sides to see if the issue follows the globe. Given that's an unlikely scenario, I'll wait until I've exhausted other options.

When I was under the truck last night, I confirmed that the connectors and visible wiring going into the Control Valve Assembly and the FL Damping Force Control Actuator are in good shape. The connectors seal properly and were very clean inside. I didn't take any measurements because I'm waiting on some better test leads. So when my leads get here, I'll follow your breakdown and test the Height Control Sensors. Both sensors up front are pretty caked up and look rough overall, so fingers crossed.

 

[suprarx7nut]

Awesome breakdown, thanks for taking the time to write that out. It's interesting that you note 1 globe could go bad, I also was having that thought. I've considered removing the front 2 globes, inspecting them, and swapping them to opposite sides to see if the issue follows the globe. Given that's an unlikely scenario, I'll wait until I've exhausted other options.

When I was under the truck last night, I confirmed that the connectors and visible wiring going into the Control Valve Assembly and the FL Damping Force Control Actuator are in good shape. The connectors seal properly and were very clean inside. I didn't take any measurements because I'm waiting on some better test leads. So when my leads get here, I'll follow your breakdown and test the Height Control Sensors. Both sensors up front are pretty caked up and look rough overall, so fingers crossed.

My guess is a bad globe. That seems to be the only thing that reliably produces a "terrible" ride. The system on sport 2 isn't unbearable, so when folks say it feels awful I immediately think bad globe. Curious to see what you find. Let us know!

 

[japansam23]

My guess is a bad globe. That seems to be the only thing that reliably produces a "terrible" ride. The system on sport 2 isn't unbearable, so when folks say it feels awful I immediately think bad globe. Curious to see what you find. Let us know!

Yeah, it seems to be most likely, but also an expensive fix. I'd like to figure out if the FL damper being stiff could be the sole cause of the terrible ride quality.

On an unrelated note, I hooked up Techstream to see what my steering angle sensors are doing because I've also read about crazy angle readings causing problems. The sensor in the AHC data tab shows 0.0 degrees with the wheels straight, but the sensor in the ABS/VSC section shows 1050.0 degrees. As far as I know, I do not have VGRS because there is no sign of it in Techstream and my vehicle is a year 2000. So to recalibrate the sensor, I tried the method discussed here where you uplug the sensor, power cycle the vehicle, then plug it back in. This did not correct the crazy reading that shows in the ABS/VSC menu. I'm wondering if this is normal or if AHC is receiving that bad reading and stiffening up the damper in response.

 

[IndroCruise]

Yeah, it seems to be most likely, but also an expensive fix. I'd like to figure out if the FL damper being stiff could be the sole cause of the terrible ride quality.

On an unrelated note, I hooked up Techstream to see what my steering angle sensors are doing because I've also read about crazy angle readings causing problems. The sensor in the AHC data tab shows 0.0 degrees with the wheels straight, but the sensor in the ABS/VSC section shows 1050.0 degrees. As far as I know, I do not have VGRS because there is no sign of it in Techstream and my vehicle is a year 2000. So to recalibrate the sensor, I tried the method discussed here where you uplug the sensor, power cycle the vehicle, then plug it back in. This did not correct the crazy reading that shows in the ABS/VSC menu. I'm wondering if this is normal or if AHC is receiving that bad reading and stiffening up the damper in response.

To obtain some further information, the following is suggested:

Go to the Factory Service Manual at:

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

This gives details relating to LC100 and not LX470 but it is still a very comprehensive resource for both lines of vehicles. There may be some differences about which features appeared in which year in the different lines of vehicles.

Then go to tab labelled:

New Car Features

Then:

CHASSIS

Then:

SUSPENSION

Then:

Active Height Control Suspension and Skyhook TEMS
(for a useful but general description only)

Then scroll further down to the tab labelled:

Repair Manual

Then within this tab, go to:

DIAGNOSTICS
(This tab contains extensive detailed information on diagnosis, testing and rectification of the vehicle systems):

Then within this tab, go to:

ACTIVE HEIGHT CONTROL & SKYHOOK TEMS

Then within this tab, go to

HOW TO PROCEED WITH TROUBLESHOOTING
(this outlines the Toyota approach to systematic diagnosis):

Then:

PRE-CHECK:

Then:

DIAGNOSTIC TROUBLE CHART:

Then:

PROBLEMS SYMPTOMS TABLE

(This is a VERY useful summary. Note the statement in the introduction to this table – “If a normal code is displayed (my translation: meaning the condition is normal without DTC appearing) during the DTC check but the problem still occurs, check the circuit for each problem symptom in the order given in the table below (meaning the PROBLEMS SYMPTOMS TABLE) and proceed to the relevant troubleshooting page”).

Then follows the Troubleshooting Pages – each gives a detailed description of a range of fault conditions, in each case providing the following headings:

CIRCUIT DESCRIPTION

“Fail-safe function”

There are a range of different “fail-safe” functions which operate when the AHC/TEMS ECU determines that it has encountered a fault condition or has received conflicting signals from various sensors. Note: Not all “fail-safe” responses are the same but many of them disable some part of the AHC/TEMS system, very often disabling the TEMS variable damping which obviously causes a rough ride, and/or, disabling the AHC raise/lower operation. An understanding of the various “fail-safe” functions is vital to understanding the various symptoms which may be experienced. This helps to understand what symptom(s) goes with what problem. The Diagnostic Trouble Code (DTC) does not always appear with every fault condition. Note that sometimes the language of the text has suffered in the translation from Japanese and can be a little unclear in some places – but mostly the idea becomes obvious.

WIRING DIAGRAM
(This is a bit dazzling but very helpful for electrically-mind IH8MUD members).

INSPECTION PROCEDURE
(This often specifies some values to measure and usually provides a short decision tree indicating suggested action).

For example, in this section go to:

C1711/11, C1713/13 Check height control sensor

OR

C1721/21, C1723/23 Damping Force Control Actuator Circuit

OR

C7181 Steering angle sensor circuit


In relation to the separate question about the relevance of the steering angle sensor input used by brake/VSC-related ECU’s, maybe the answers can be found by perusing the relevant sections of the FSM as suggested below. (My understanding is that the AHC/TEMS ECU is satisfied with its own steering angle input as described above – but more knowledgeable IH8MUD Members may be able to provide more clarity):

Return to the tab labelled:

DIAGNOSTICS

Then within this tab, go to:

ANTI-LOCK BRAKING SYSTEM (2000.8 - )

Also within this tab, go to:

ABS & VEHICLE STABILITY CONTROL (VSC) & BRAKE ASSIST (BA) SYSTEM

Also within this tab, go to:

DIAGNOSTIC TROUBLE CODE CHARTS (for different model years)

Also within this tab, go to:

PROBLEM SYMPTOMS TABLE (for different model years)

And then follows a long list of detailed DTCs

Suggest go to

C1231 /31 (1998.8 - ) Steering Angle Sensor Circuit


If your vehicle has VGRS, go further down to:

VARIABLE GEAR RATIO STEERING



That is probably more than enough reading for one weekend!!

 

[japansam23]

To obtain some further information, the following is suggested:

Go to the Factory Service Manual at:

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

This gives details relating to LC100 and not LX470 but it is still a very comprehensive resource for both lines of vehicles. There may be some differences about which features appeared in which year in the different lines of vehicles.

Then go to tab labelled:

New Car Features

Then:

CHASSIS

Then:

SUSPENSION

Then:

Active Height Control Suspension and Skyhook TEMS
(for a useful but general description only)

Then scroll further down to the tab labelled:

Repair Manual

Then within this tab, go to:

DIAGNOSTICS
(This tab contains extensive detailed information on diagnosis, testing and rectification of the vehicle systems):

Then within this tab, go to:

ACTIVE HEIGHT CONTROL & SKYHOOK TEMS

Then within this tab, go to

HOW TO PROCEED WITH TROUBLESHOOTING
(this outlines the Toyota approach to systematic diagnosis):

Then:

PRE-CHECK:

Then:

DIAGNOSTIC TROUBLE CHART:

Then:

PROBLEMS SYMPTOMS TABLE

(This is a VERY useful summary. Note the statement in the introduction to this table – “If a normal code is displayed (my translation: meaning the condition is normal without DTC appearing) during the DTC check but the problem still occurs, check the circuit for each problem symptom in the order given in the table below (meaning the PROBLEMS SYMPTOMS TABLE) and proceed to the relevant troubleshooting page”).

Then follows the Troubleshooting Pages – each gives a detailed description of a range of fault conditions, in each case providing the following headings:

CIRCUIT DESCRIPTION

“Fail-safe function”

There are a range of different “fail-safe” functions which operate when the AHC/TEMS ECU determines that it has encountered a fault condition or has received conflicting signals from various sensors. Note: Not all “fail-safe” responses are the same but many of them disable some part of the AHC/TEMS system, very often disabling the TEMS variable damping which obviously causes a rough ride, and/or, disabling the AHC raise/lower operation. An understanding of the various “fail-safe” functions is vital to understanding the various symptoms which may be experienced. This helps to understand what symptom(s) goes with what problem. The Diagnostic Trouble Code (DTC) does not always appear with every fault condition. Note that sometimes the language of the text has suffered in the translation from Japanese and can be a little unclear in some places – but mostly the idea becomes obvious.

WIRING DIAGRAM
(This is a bit dazzling but very helpful for electrically-mind IH8MUD members).

INSPECTION PROCEDURE
(This often specifies some values to measure and usually provides a short decision tree indicating suggested action).

For example, in this section go to:

C1711/11, C1713/13 Check height control sensor

OR

C1721/21, C1723/23 Damping Force Control Actuator Circuit

OR

C7181 Steering angle sensor circuit


In relation to the separate question about the relevance of the steering angle sensor input used by brake/VSC-related ECU’s, maybe the answers can be found by perusing the relevant sections of the FSM as suggested below. (My understanding is that the AHC/TEMS ECU is satisfied with its own steering angle input as described above – but more knowledgeable IH8MUD Members may be able to provide more clarity):

Return to the tab labelled:

DIAGNOSTICS

Then within this tab, go to:

ANTI-LOCK BRAKING SYSTEM (2000.8 - )

Also within this tab, go to:

ABS & VEHICLE STABILITY CONTROL (VSC) & BRAKE ASSIST (BA) SYSTEM

Also within this tab, go to:

DIAGNOSTIC TROUBLE CODE CHARTS (for different model years)

Also within this tab, go to:

PROBLEM SYMPTOMS TABLE (for different model years)

And then follows a long list of detailed DTCs

Suggest go to

C1231 /31 (1998.8 - ) Steering Angle Sensor Circuit


If your vehicle has VGRS, go further down to:

VARIABLE GEAR RATIO STEERING



That is probably more than enough reading for one weekend!!

Wow, that link is a treasure trove. What publication is that exactly? I have Vol. 1 and 2 and the EWD for my exact year Lexus, but I don't think it has any of the detailed system decriptions or diagnosis sections. I'm still trying to find out how Techstream could be reporting 2 different angle readings in different sections, so I'll use this new info to try to learn more about the system overall.

 

[IndroCruise]

Wow, that link is a treasure trove. What publication is that exactly? I have Vol. 1 and 2 and the EWD for my exact year Lexus, but I don't think it has any of the detailed system decriptions or diagnosis sections. I'm still trying to find out how Techstream could be reporting 2 different angle readings in different sections, so I'll use this new info to try to learn more about the system overall.

Published by Toyota Motor Corporation -- OVERSEAS CUSTOMER SERVICE TECHNICAL DIVISION – and brought to attention by @Moridinbg at this post:

Improved FSM downloads

See also some alternatives above and below this post in the same string.

Personally, I find the https://lc100e.github.io/manual/ to be the most comprehensive source for LC100/LC105 and with a lot of common ground with LX470. It does take a little while to adjust to the way the document works, but once it becomes familiar, navigation is straightforward.

 

[IndroCruise]

On an unrelated note, I hooked up Techstream to see what my steering angle sensors are doing because I've also read about crazy angle readings causing problems. The sensor in the AHC data tab shows 0.0 degrees with the wheels straight, but the sensor in the ABS/VSC section shows 1050.0 degrees. As far as I know, I do not have VGRS because there is no sign of it in Techstream and my vehicle is a year 2000. So to recalibrate the sensor, I tried the method discussed here where you uplug the sensor, power cycle the vehicle, then plug it back in. This did not correct the crazy reading that shows in the ABS/VSC menu. I'm wondering if this is normal or if AHC is receiving that bad reading and stiffening up the damper in response.

i don't have an answer for the question concerning the different steering angle responses used by the ABS/VSC-related ECU versus the input used by the AHC ECU -- let's put it out there requesting advice from @PADDO or @uHu or others able to contribute.

 

[uHu]

Yeah, it seems to be most likely, but also an expensive fix. I'd like to figure out if the FL damper being stiff could be the sole cause of the terrible ride quality.

On an unrelated note, I hooked up Techstream to see what my steering angle sensors are doing because I've also read about crazy angle readings causing problems. The sensor in the AHC data tab shows 0.0 degrees with the wheels straight, but the sensor in the ABS/VSC section shows 1050.0 degrees. As far as I know, I do not have VGRS because there is no sign of it in Techstream and my vehicle is a year 2000. So to recalibrate the sensor, I tried the method discussed here where you uplug the sensor, power cycle the vehicle, then plug it back in. This did not correct the crazy reading that shows in the ABS/VSC menu. I'm wondering if this is normal or if AHC is receiving that bad reading and stiffening up the damper in response.

The FSM Diagnostic section has some info on the steering angle input to the VSC system, and how it is connected. The circuit and ECU differs depending on the month of production. On a MY 2000, do you actually have VSC?

 

[japansam23]

Just wanted to provide an update to the thread. I purchased new accumulator globes from an Ebay seller called JDM Planet. I went straight to the globes rather than doing in-depth electrical troubleshooting because I made up my mind to gut the system and put in a traditional lift if the globes turned out to not be the culprit. I do not enjoy chasing electrical gremlins, and this seemed to be a practical course of action, for the long term health of my wallet and sanity.

With a fresh fluid flush and new accumulator globes, there was no noticeable change in ride quality. I verified all pressures and levelling measurements again, and all were still squarely within spec. I still have the stiff front left damper when I do the 16 step damper test, so it's possible that there is an electrical fault somewhere that is not throwing a code, or that corner's shock and/or accumulator has failed. Also, Techstream still gives 2 different steering angle readings, one of which I cannot reset to zero. The unanswered questions are frustrating because I can't really offer much to others that are having similar issues.

TL;DR - New accumulator globes did not fix my rough ride. An Ironman Foam Cell Stage 2 kit is on the way and should be here next week.

 

[uHu]

As the globe is ruled out, there's only 2 components left, considering it unlikely that this is an electronic failure. Those 2 are the shock and the actuator valves. You can easily check both by opening the bleader valve, and then check that that corner moves freely. Alternatively also detach the bottom shock bolt to see that the shock moves freely. That could also give some indication of whether it is a mechanical constriction of the shock, or something blocking the passage of fluid through the actuator.
I see that you have chickend out, so this might not be relevant even if it takes only 5 mins ?

 

[japansam23]

As the globe is ruled out, there's only 2 components left, considering it unlikely that this is an electronic failure. Those 2 are the shock and the actuator valves. You can easily check both by opening the bleader valve, and then check that that corner moves freely. Alternatively also detach the bottom shock bolt to see that the shock moves freely. That could also give some indication of whether it is a mechanical constriction of the shock, or something blocking the passage of fluid through the actuator.
I see that you have chickend out, so this might not be relevant even if it takes only 5 mins ?

Do you mean the bleeder at the accumulator? If I open that won't the truck drop down to bump stops?

 

[uHu]

Do you mean the bleeder at the accumulator? If I open that won't the truck drop down to bump stops?

Yes, if you don't put it on stands first. If it does drop, you know that the shock and the hydraulic line to the bleeder is not obstructed. If the right side also moves freely when opening the left bleeder, you know that the lines are OK all the way. The only thing left then is the actuator operation.
What I don't know is if the bleeder is on the globe side or on the shock side of the actuator valves.

 

[japansam23]

Yes, if you don't put it on stands first. If it does drop, you know that the shock and the hydraulic line to the bleeder is not obstructed. If the right side also moves freely when opening the left bleeder, you know that the lines are OK all the way. The only thing left then is the actuator operation.
What I don't know is if the bleeder is on the globe side or on the shock side of the actuator valves.

Ok, yeah, when I bleed fluid it depressurizes the whole front system as it should, and both sides drop. I considered finding a known good actuator to test out, but I've since "chickened out". Traditional suspension fits into my long term goals with the truck anyway so I'm not too broken up about it.