AHC pressures

[Magnaman]

• "I presume my front pressure is way too high as well?" Definitely Yes -- as menioned in my Post #17 above. This over-pressure is a recipe for internal seals leaking in the 'shock absorbers'. Unless seals have been permanently damaged by long term over-pressure, leaks may stop when AHC pressures are corrected.

• Given the AHC pressures reported, it is unsurprising that ".... driving over over washboard and bad roads the suspension feels too stiff". At your AHC pressures, damping and 'ride quality' are compromised. This will improve when Front and Rear AHC pressures are corrected into the FSM-specified ranges and damping can operate correctly as designed.

• Good that AHC is still working -- means that the ECU has not initiated "Fail Safe Function" and caused AHC/TEMS prohibitions -- so maybe TEMS is working as well. To confirm that TEMS is working, drive (safely) with your scanner connected. If your scanner displays something similar to "Front Wheel Step" and "Rear Wheel Step", also "Damping Force Switch 1" and "Damping Force Switch 2", then you should be able to see differences while driving and also see the effects of changing the COMFORT switch on the Centre Console through its four positions. This should show the variations in up to 16 steps in damping positions which the ECU (TEMS) can adopt in real time. When stopped or in "Fail Safe Mode" TEMS will default to Step 8 and there will be no adaptive damping with different road conditions.

• It is worth remainings suspicious of the Rear Height Sensor circuit (not just the Sensor), as the ECU does not distinguish between faults in the Sensor, or the Connectot, or the Harness. It is common for a fault to arise which causes the wrong voltage signal for the actual height of the vehicle to be sent to ECU -- but the signal remains within the range of 0.3 Volts to 4.7 Volts accepted by by the ECU. In this situation, no DTC is recorded (because the signal is within range accepted by the ECU) even though there is a fault somewhere in the Sensor circuit or in the Sensor itself -- such as when the circuit is shortened in some way, lowering resistance and affecting the signal voltage. Diagnosis of Height Control Sensor circuit faults also requires observation of the behaviour of the vehicle -- especially when Height Control Sensor circuit readings on Techstream or other scanner are inconsistent with the physical tape-measured hub-to-fender distances -- as in the case of your vehicle. This is one of the limitations of the AHC/TEMS Diagnostics.

View attachment 4072388

View attachment 4072389

Yes I found it in the D7. They call it front and rear wheel "step". In the graph it's very in constantly bas I drive and also changes with the comfort selector, so I assume it's working. I was going to send you a live data report including those and the height sensors and pressures, but I don't know how to send it yet. I've asked Xtool. I did find the rear ride height sensor. When I have time, I will pull it and test it as well as the circuit and the wiring and be back to you. I meant to correct myself that there's not really a leak at the front shocks, more like a seepage (I have added no fluid in years). However, I did the graduation test on the tank today and I think it's only seven or eight marks which is not good, although I haven't changed the fluid in three or four years. Thanks again, you are truly a wizard!

 

[Magnaman]

So just measure hub to fender and ignore the tire size?

Exactly.

 

[jaewastooshort]

Bonjour,

Merci pour toutes ces informations, qui me permettent de maintenir la suspension AHC de mon Land Cruiser 100 diesel de 2004 avec 227 000 km au compteur en parfait état !

Deux questions, s'il vous plaît :
La pression à l'avant est correcte (6,8 MPa). La pression à l'arrière est un peu élevée (6,8 MPa). Je vais donc utiliser des entretoises de 30 mm pour l'abaisser. Connaissez-vous le couple de serrage de l'écrou inférieur de l'amortisseur ?

Je ne constate aucune différence entre les modes d'amortissement « confort » et « sport ». Quelle pourrait en être la cause ?
Pour information, le capteur avant droit est à 1,8 mm, le gauche à -1 mm et le capteur arrière à 1 mm. La hauteur des moyeux de roue est correcte (500 mm à l'avant, 520 mm à l'arrière), les sphères de suspension sont neuves (14 points au test) et le liquide de suspension AHC a été changé.

Merci pour vos commentaires.

1) I'm not sure what the torque specification is for the shock nut, but I have seen it posted before, along with links to the factory service manual (FSM), though I think I've only seen those files/links posted to english versions. FSM should have all the torque info though.

2) When you mention noticing difference in the modes, a scan should show a difference when selected as the four modes basically just modify the combination of valves used for shock operation. As far as driving feel, I mostly notice it in body roll and how much the vehicle bounces going over speed bumps, but I have also noticed that if shock pressures are too high it can have a significant impact on how effective that suspension mode setting is (effectiveness seems to decrease the further out of spec the pressures are)

 

[jaewastooshort]

Yes I found it in the D7. They call it front and rear wheel "step".

I just ordered a D7S which should be here tomorrow. Last time I tried to get techstream up on the same laptop I've used previously I ran into nothing but problems and gave up after 2 hours. I may have questions for you once it gets here, but hoping it'll be way more straight-forward that all the hoop-jumping associated with running techstream on a VM.

I'm really hoping the D7S will be able to help with the airbag light on my corvette as well, because otherwise I would have just gone with one of the cheaper bi-directional toyota-specific scanners

 

[Magnaman]

I just ordered a D7S which should be here tomorrow. Last time I tried to get techstream up on the same laptop I've used previously I ran into nothing but problems and gave up after 2 hours. I may have questions for you once it gets here, but hoping it'll be way more straight-forward that all the hoop-jumping associated with running techstream on a VM.

I'm really hoping the D7S will be able to help with the airbag light on my corvette as well, because otherwise I would have just gone with one of the cheaper bi-directional toyota-specific scanners

I'll be happy to help if I can with your D7. As far as the AHC data goes it was easy.

 

[IndroCruise]

Bonjour,

Merci pour toutes ces informations, qui me permettent de maintenir la suspension AHC de mon Land Cruiser 100 diesel de 2004 avec 227 000 km au compteur en parfait état !

Deux questions, s'il vous plaît :
La pression à l'avant est correcte (6,8 MPa). La pression à l'arrière est un peu élevée (6,8 MPa). Je vais donc utiliser des entretoises de 30 mm pour l'abaisser. Connaissez-vous le couple de serrage de l'écrou inférieur de l'amortisseur ?

Je ne constate aucune différence entre les modes d'amortissement « confort » et « sport ». Quelle pourrait en être la cause ?
Pour information, le capteur avant droit est à 1,8 mm, le gauche à -1 mm et le capteur arrière à 1 mm. La hauteur des moyeux de roue est correcte (500 mm à l'avant, 520 mm à l'arrière), les sphères de suspension sont neuves (14 points au test) et le liquide de suspension AHC a été changé.

Merci pour vos commentaires.

For @Marc74 -- hopefully Google Translator from French to English has not offended the French language -- replies are interploated in bold italics in the English translation below:

++++++++++
Hello,

Thank you for all this information, which allows me to keep the AHC suspension on my 2004 Land Cruiser 100 diesel with 227,000 km on the odometer in perfect condition!

Great to read of another LC100 with 1HD-FTE and AHC/TEMS surviving! At 227,000km (141,000 miles) and 2004 vintage it is still young, a treasure worth preserving.

Two questions, please:
The front pressure is correct (6.8 MPa). The rear pressure is a little high (6.8 MPa). I'm therefore going to use 30 mm spacers to lower it. Do you know the tightening torque for the lower shock absorber nut?

For the requested details, suggest go to this link
LC100 Workshop Manual - https://lc100e.github.io/
then scroll through the Index panel to
+ Repair Manual
+ SUSPENSION AND AXLE
+ COIL SPRING AND REAR SHOCK ABSORBER (Independent Front Suspension)
+ COMPONENTS -- shows torque details
+ REMOVAL -- shows torque details
+ INSTALLATION -- mentions that installation settings -- including torque details -- are the same for INSTALLATION and REMOVAL

I don't notice any difference between the "comfort" and "sport" damping modes. What could be the cause?

The reported details for your AHC system and TEMS system appear to be healthy. There are no obvious reasons to expect "Fail Safe Function" which would prohibit operation of the AHC and TEMS systems. The fact that the vehicle can be moved from "LO" height to "N" height to measure AHC pressures also indicates that the system is functioning. No Diagnostic Trouble Codes (DTC's) are mentioned, the vehicle physical tape-measured heights are correct at Front and Rear, the AHC pressures are reasonable, and the 'globes' are in good condition with 14 graduations between "LO" height and "HI" height at the AHC Tank under the FSM-prescribed conditions. Therefore good damping performance and good 'ride quality' should be expected -- unless there is some obscure fault.

The different ride effects from the four settings at the COMFORT switch can be subtle, especially if the vehicle is very heavy -- but should be discernable.

If there is no difference at the COMFORT settings, suggest start with simple things first ....

Check the COMFORT switch -- go to this link
LC100 Workshop Manual - https://lc100e.github.io/
then scroll through the Index panel to
+ Repair Manual
+ DIAGNOSTICS
+ ACTIVE HEIGHT CONTROL SUSPENSION & SKYHOOK TEMS
+ C1786
+ C1787
+ C1788

As a starting point, use a plastic trim tool or maybe a screw-driver with tape on the blade tip and pop open the switch to expose the internal contacts. Try cleaning the contacts with the eraser on a pencil and then a cotton bud or similar with with rubbing alcohol -- something that cleans then evaporates without leaving residue.

Posssibly consider a replacement AHC Console Switch Toyota/Lexus Part Number 89299-60020 (IMPEX USD57.10 plus freight, duties, tariffs, taxes).

Checking the centre console switch is not too difficult -- guided by the above references:

• Check output signal of damping mode select switch,
• Check damping mode select switch.

If the problem continues after these "simple tests", then please report back. It may be that the next step is to investigate the Damping Force Control Actuator circuits (meaning Actuators and Connectors and Harness).

In addition, as mentioned in Post #18 this thread, to check that the Toyota Electronically Modulated Suspension (TEMS) system actually is working, drive with Techstream (or other scanner) hooked up and you should observe the two values labeled STEP in the AHC data list. These values will change in real time, making active damping adjustments for speed, COMFORT switch settings, and road conditions. They should both be “8” with the vehicle not moving then start to change up and down as you drive -- in the range "1" (soft) to "16" (hard), depending on settings and actual road conditions. Front STEP and rear STEP won’t necessarily be the same.

For your information, the front right sensor is at 1.8 mm, the left at -1 mm, and the rear sensor at 1 mm. The wheel hub height is correct (500 mm front, 520 mm rear), the suspension spheres are new (14 points on the test), and the AHC suspension fluid has been changed.

Thank you for your feedback.
+++++++++

 

[Marc74]

Un grand merci IndroCruise d'avoir pris le temps de me répondre avec autant de précision ! Merci également pour le lien du manuel de réparation que je ne possédais pas ! Je vais suivre vos conseils et commencer par vérifier le commutateur d'amortissement. Je vous tiendrai informé.
Le 1HT-FTE est vraiment un bon moteur !
Cordialement.

 

[Marc74]

Un grand merci IndroCruise d'avoir pris le temps de me répondre avec autant de précision ! Merci également pour le lien du manuel de réparation que je ne possédais pas ! Je vais suivre vos conseils et commencer par vérifier le commutateur d'amortissement. Je vous tiendrai informé.
Le 1HT-FTE est vraiment un bon moteur !
Cordialement.

 

[Marc74]

Je pense avoir trouvé la raison pour laquelle il n'y a pas de différence entre les modes d'amortissement "confort" et "sport" grâce aux photos et explications données par IndroCruise.
En démontant le commutateur d'amortissement j'ai constaté que les petits balais métalliques (deuxième photo du message 26) n'étaient plus sur la roue blanche en plastique qu'actionne le bouton du commutateur. Je les ai remis en place comme sur la photo et j'ai nettoyé les pistes de contact.
Je fais un essai demain...
Encore merci IndroCruise

 

[jaewastooshort]

... hoping it'll be way more straight-forward that all the hoop-jumping associated with running techstream on a VM.

man, so much easier than wrestling tech stream...

these were taken after going L to N (first screen shot) , then H to N to L and back to N (2nd shot). I've got on my RTT, rear 5th wheel swing out, and winch on front, but otherwise unloaded.

Looks like I need to adjust driver's side TB a bit to level the left-to-right front, but otherwise pretty happy with these

 

[Magnaman]

• "I presume my front pressure is way too high as well?" Definitely Yes -- as menioned in my Post #17 above. This over-pressure is a recipe for internal seals leaking in the 'shock absorbers'. Unless seals have been permanently damaged by long term over-pressure, leaks may stop when AHC pressures are corrected.

• Given the AHC pressures reported, it is unsurprising that ".... driving over over washboard and bad roads the suspension feels too stiff". At your AHC pressures, damping and 'ride quality' are compromised. This will improve when Front and Rear AHC pressures are corrected into the FSM-specified ranges and damping can operate correctly as designed.

• Good that AHC is still working -- means that the ECU has not initiated "Fail Safe Function" and caused AHC/TEMS prohibitions -- so maybe TEMS is working as well. To confirm that TEMS is working, drive (safely) with your scanner connected. If your scanner displays something similar to "Front Wheel Step" and "Rear Wheel Step", also "Damping Force Switch 1" and "Damping Force Switch 2", then you should be able to see differences while driving and also see the effects of changing the COMFORT switch on the Centre Console through its four positions. This should show the variations in up to 16 steps in damping positions which the ECU (TEMS) can adopt in real time. When stopped or in "Fail Safe Mode" TEMS will default to Step 8 and there will be no adaptive damping with different road conditions.

• It is worth remainings suspicious of the Rear Height Sensor circuit (not just the Sensor), as the ECU does not distinguish between faults in the Sensor, or the Connectot, or the Harness. It is common for a fault to arise which causes the wrong voltage signal for the actual height of the vehicle to be sent to ECU -- but the signal remains within the range of 0.3 Volts to 4.7 Volts accepted by by the ECU. In this situation, no DTC is recorded (because the signal is within range accepted by the ECU) even though there is a fault somewhere in the Sensor circuit or in the Sensor itself -- such as when the circuit is shortened in some way, lowering resistance and affecting the signal voltage. Diagnosis of Height Control Sensor circuit faults also requires observation of the behaviour of the vehicle -- especially when Height Control Sensor circuit readings on Techstream or other scanner are inconsistent with the physical tape-measured hub-to-fender distances -- as in the case of your vehicle. This is one of the limitations of the AHC/TEMS Diagnostics.

View attachment 4072388

View attachment 4072389

I just discovered I have not changed my AHC fluid in 8 years and 60K miles! Time flies. I better do this first.

 

[Wilsil]

I need to re-visit my AHC system as the ride is getting bouncy.
Still on original globes, which has done 329,800 kms, many kms on some hard tracks.
The rear springs have been replaced with LC non-AHC springs many years ago, AHC fluid has been replaced 3 years ago.
It goes form N to L and from N to H without too much problem, even with the additional weight my car has.
The only thing is that I am not sure the comfy to sport setting is doing anything.

I have to hook up Techstream again and check the pressures, gradients and heights.

 

[Magnaman]

• "I presume my front pressure is way too high as well?" Definitely Yes -- as menioned in my Post #17 above. This over-pressure is a recipe for internal seals leaking in the 'shock absorbers'. Unless seals have been permanently damaged by long term over-pressure, leaks may stop when AHC pressures are corrected.

• Given the AHC pressures reported, it is unsurprising that ".... driving over over washboard and bad roads the suspension feels too stiff". At your AHC pressures, damping and 'ride quality' are compromised. This will improve when Front and Rear AHC pressures are corrected into the FSM-specified ranges and damping can operate correctly as designed.

• Good that AHC is still working -- means that the ECU has not initiated "Fail Safe Function" and caused AHC/TEMS prohibitions -- so maybe TEMS is working as well. To confirm that TEMS is working, drive (safely) with your scanner connected. If your scanner displays something similar to "Front Wheel Step" and "Rear Wheel Step", also "Damping Force Switch 1" and "Damping Force Switch 2", then you should be able to see differences while driving and also see the effects of changing the COMFORT switch on the Centre Console through its four positions. This should show the variations in up to 16 steps in damping positions which the ECU (TEMS) can adopt in real time. When stopped or in "Fail Safe Mode" TEMS will default to Step 8 and there will be no adaptive damping with different road conditions.

• It is worth remainings suspicious of the Rear Height Sensor circuit (not just the Sensor), as the ECU does not distinguish between faults in the Sensor, or the Connectot, or the Harness. It is common for a fault to arise which causes the wrong voltage signal for the actual height of the vehicle to be sent to ECU -- but the signal remains within the range of 0.3 Volts to 4.7 Volts accepted by by the ECU. In this situation, no DTC is recorded (because the signal is within range accepted by the ECU) even though there is a fault somewhere in the Sensor circuit or in the Sensor itself -- such as when the circuit is shortened in some way, lowering resistance and affecting the signal voltage. Diagnosis of Height Control Sensor circuit faults also requires observation of the behaviour of the vehicle -- especially when Height Control Sensor circuit readings on Techstream or other scanner are inconsistent with the physical tape-measured hub-to-fender distances -- as in the case of your vehicle. This is one of the limitations of the AHC/TEMS Diagnostics.

View attachment 4072388

View attachment 4072389

IndroCruise, I have made great headway. The torsion bars were so far off as you said. Huge difference in ride quality! Got my pressures down to around 7 front and rear. Heights are good except right rear still is about half an inch high for some reason that I cannot determine. With the heights and pressures pretty good, I cannot get the rear height sensor reading below around 13 mm. I don't quite understand it. The sensor is clearly "working" since it goes from -56mm to + 23mm when going from H to L. I've checked out the wiring and plug. I played around with the sensor adjustment. I don't get it. It's almost like it needs to be calibrated. My D7 scanner has this special function called "height offset". I'm wondering if that's a calibration function, but I didn't want to mess with it without talking with you first. I was going to remove the sensor and test it but I stopped because I there is this plastic retainer that holds the cable onto the sensor that I wasn't sure how to deal with and I didn't want to break it.

 

[IndroCruise]

IndroCruise, I have made great headway. The torsion bars were so far off as you said. Huge difference in ride quality! Got my pressures down to around 7 front and rear. Heights are good except right rear still is about half an inch high for some reason that I cannot determine. With the heights and pressures pretty good, I cannot get the rear height sensor reading below around 13 mm. I don't quite understand it. The sensor is clearly "working" since it goes from -56mm to + 23mm when going from H to L. I've checked out the wiring and plug. I played around with the sensor adjustment. I don't get it. It's almost like it needs to be calibrated. My D7 scanner has this special function called "height offset". I'm wondering if that's a calibration function, but I didn't want to mess with it without talking with you first. I was going to remove the sensor and test it but I stopped because I there is this plastic retainer that holds the cable onto the sensor that I wasn't sure how to deal with and I didn't want to break it.

The basis principle of the Active Height Control (AHC) system is that during fault-free vehicle operation the Suspension Electronic Control Unit (ECU) will use voltage signals from the Height Control Sensors to cause the Levelling Valves and the AHC Pump to 'actively' return the vehicle to the position matching the set voltage signal from Height Control Sensors for "N" height (or "LO" height or "HI" height as selected by the driver at the at the console switch).

The FSM test procedure indicates these 'set points'. These 'set points' are fixed in the ECU and are not adjustable.

The Height Control Sensors are simple potentiometers. They use the variation in resistance provided by the length of the slider path inside the Sensor to vary the voltage output. In that way, causing a voltage signal varies with the position of the arm which mechanically links the chassis to a moving part of the suspension -- specifically, the Left Hand Rear Upper Control Arm in the case of the Rear suspension.

There is nothing 'electronic' inside the actual Height Control Sensors used in LC100 and LX470.

There is nothing adjustable inside the Sensor nor inside the ECU. Adjustment is achieved by adjustiing the position of the mechanical connection as shown in the picture below.

Techstream (or other scanner such as Xtool D7) does not display the voltage signals. Instead, the voltages are converted to readings displayed in inches or millimetres of variance from the neutral postion, meaning zero at "N" height, with FSM-specified tolerance of +/- 5 millimetres or +/- 0.2 inches.

As Height Control Sensors age and slowly deteriorate over time, the continuity and/or resistance along the carbon path, the internal connectors, and the contact pressure applied by the tiny contact brushes all deteriorate. This will be accelerated if there has been moisture ingress. On opening of the Sensor, this deterioration may not be obvious to the naked eye -- inspection is insufficient. Testing per FSM is essential as a minimum. As explained in the fourth bullet point and FSM extract at Post #18 this thread, this deterioration may not be sufficient to initiate a Diagnostic Trouble Code (DTC) if the output voltage signal is still within the FSM-specified range accepted by the ECU -- EVEN THOUGH the voltage signal is incorrect for the actual height of the vehicle. (This is why it is always important to quote tape-measured hub-to-fender heights when reviewing Height Control Sensor readings from Techstream or other scanners).

Your persistent non-zero, out-of-tolerance Rear Height Control Sensor reading indicates

• EITHER that the condition of the Sensor is deteriorating (it MAY respond to cleaning but replacement with a new genuine Toyota/Lexus Sensor is the more reliable solution),
• OR, there is a fault in the connector or in the harness wiring (possibly close to the connector).

Suggest proceed with inspection and cleaning as a first step.

 

[Magnaman]

Thanks. I will pull the sensor completely open it up and see if it needs cleaning and then I will test it with the batteries. Could just be worried out at 240k miles. Should the front and rear pressures be changing on my scanner as I'm driving? They are not. For each height sensor reading in millimeters the scanner has some ability set the "reference" point. What does this mean?

 

[Magnaman]

The basis principle of the Active Height Control (AHC) system is that during fault-free vehicle operation the Suspension Electronic Control Unit (ECU) will use voltage signals from the Height Control Sensors to cause the Levelling Valves and the AHC Pump to 'actively' return the vehicle to the position matching the set voltage signal from Height Control Sensors for "N" height (or "LO" height or "HI" height as selected by the driver at the at the console switch).

The FSM test procedure indicates these 'set points'. These 'set points' are fixed in the ECU and are not adjustable.

View attachment 4097278

The Height Control Sensors are simple potentiometers. They use the variation in resistance provided by the length of the slider path inside the Sensor to vary the voltage output. In that way, causing a voltage signal varies with the position of the arm which mechanically links the chassis to a moving part of the suspension -- specifically, the Left Hand Rear Upper Control Arm in the case of the Rear suspension.

There is nothing 'electronic' inside the actual Height Control Sensors used in LC100 and LX470.

There is nothing adjustable inside the Sensor nor inside the ECU. Adjustment is achieved by adjustiing the position of the mechanical connection as shown in the picture below.

View attachment 4097264

View attachment 4097293

Techstream (or other scanner such as Xtool D7) does not display the voltage signals. Instead, the voltages are converted to readings displayed in inches or millimetres of variance from the neutral postion, meaning zero at "N" height, with FSM-specified tolerance of +/- 5 millimetres or +/- 0.2 inches.

As Height Control Sensors age and slowly deteriorate over time, the continuity and/or resistance along the carbon path, the internal connectors, and the contact pressure applied by the tiny contact brushes all deteriorate. This will be accelerated if there has been moisture ingress. On opening of the Sensor, this deterioration may not be obvious to the naked eye -- inspection is insufficient. Testing per FSM is essential as a minimum. As explained in the fourth bullet point and FSM extract at Post #18 this thread, this deterioration may not be sufficient to initiate a Diagnostic Trouble Code (DTC) if the output voltage signal is still within the FSM-specified range accepted by the ECU -- EVEN THOUGH the voltage signal is incorrect for the actual height of the vehicle. (This is why it is always important to quote tape-measured hub-to-fender heights when reviewing Height Control Sensor readings from Techstream or other scanners).

Your persistent non-zero, out-of-tolerance Rear Height Control Sensor reading indicates

• EITHER that the condition of the Sensor is deteriorating (it MAY respond to cleaning but replacement with a new genuine Toyota/Lexus Sensor is the more reliable solution),
• OR, there is a fault in the connector or in the harness wiring (possibly close to the connector).

Suggest proceed with inspection and cleaning as a first step.

View attachment 4097265

View attachment 4097277

View attachment 4097285

Indrocruise I am stumped. I changed my AHC fluid. With torsion bar adjustments I got the pressures down to about 6.7 in the front and around the same in the rear. Still had -14 mm rear ride height at neutral setting on my D7. I found that if I unbolted the adjustable arm from the slot in the frame I could get it to zero out on the D7 but it had to move beyond the travel capable of when still connected to the slot. I opened it up it looked perfect but as you said visual inspection is not enough and it's got 21 years and 240k miles on it, . so I got a brand new Aisin rear sensor. Still the same thing: with the hub to fender heights set properly I still have about -14 mm on the rear height at N setting. It goes very positive and very negative respectively when going from H to L. If I go under there with the engine running height set N, as I slide the arm up the slot, once it's about 3/4 of the way up the vehicle rises. It needs to be almost near the top to get the proper hub to fender height in the rear. So, pressures are pretty good, hub to fender heights are close to spec but I'm still at about -14 mm rear ride height.

 

[BVV4]

Indrocruise I am stumped. I changed my AHC fluid. With torsion bar adjustments I got the pressures down to about 6.7 in the front and around the same in the rear. Still had -14 mm rear ride height at neutral setting on my D7. I found that if I unbolted the adjustable arm from the slot in the frame I could get it to zero out on the D7 but it had to move beyond the travel capable of when still connected to the slot. I opened it up it looked perfect but as you said visual inspection is not enough and it's got 21 years and 240k miles on it, . so I got a brand new Aisin rear sensor. Still the same thing: with the hub to fender heights set properly I still have about -14 mm on the rear height at N setting. It goes very positive and very negative respectively when going from H to L. If I go under there with the engine running height set N, as I slide the arm up the slot, once it's about 3/4 of the way up the vehicle rises. It needs to be almost near the top to get the proper hub to fender height in the rear. So, pressures are pretty good, hub to fender heights are close to spec but I'm still at about -14 mm rear ride height.

I have the same problem with the rear suspension: it's always stuck at -10-12 mm, while the front sensors are reading 0. The rear sensor readings correspond to the actual height, meaning the distance from the center of the hub to the fender (48-51 cm) is 10-12 mm less than it should be. If I stand on the rear of the car (weight it), the car levels out again to -10-12 mm. I replaced the sensor with a different one, but the problem persists. I also replaced the hydraulic accumulators with new ones from Japan. The wiring is intact, otherwise the control unit would be sending incorrect data about the rear sensor to the computer. I've now ordered a new hydraulic suspension pump; it might be the cause, as the car rises from left to right in 19 seconds, while it should take up to 15 seconds. What else could it be? Why doesn't the rear of the car rise to the sensor reading of 0?

 

[Magnaman]

I have the same problem with the rear suspension: it's always stuck at -10-12 mm, while the front sensors are reading 0. The rear sensor readings correspond to the actual height, meaning the distance from the center of the hub to the fender (48-51 cm) is 10-12 mm less than it should be. If I stand on the rear of the car (weight it), the car levels out again to -10-12 mm. I replaced the sensor with a different one, but the problem persists. I also replaced the hydraulic accumulators with new ones from Japan. The wiring is intact, otherwise the control unit would be sending incorrect data about the rear sensor to the computer. I've now ordered a new hydraulic suspension pump; it might be the cause, as the car rises from left to right in 19 seconds, while it should take up to 15 seconds. What else could it be? Why doesn't the rear of the car rise to the sensor reading of 0?

Very interesting to hear that I am not the only one with this issue. Not exactly clear on what you're saying: on mine the actual hub defender distances are spot on when I slide the sensor most of the way up in the slot, but it still reads around - 14. Hopefully Indro will jump in and shed some light on this. What I did find at least with the original sensor is that if plugged in to the vehicle but unbolted from the vehicle, I could zero it out on my scanner, but it would have to move beyond the range of travel possible when installed. that is where my -14 mm comes from. I can't see how it's a wiring harness issue since as you say, everything else seems to work. My D7 scanner has certain height recalibration settings but I'm not sure how to use them. I'm wondering if it's a calibration problem.

 

[BVV4]

Very interesting to hear that I am not the only one with this issue. Not exactly clear on what you're saying: on mine the actual hub defender distances are spot on when I slide the sensor most of the way up in the slot, but it still reads around - 14. Hopefully Indro will jump in and shed some light on this. What I did find at least with the original sensor is that if plugged in to the vehicle but unbolted from the vehicle, I could zero it out on my scanner, but it would have to move beyond the range of travel possible when installed. that is where my -14 mm comes from. I can't see how it's a wiring harness issue since as you say, everything else seems to work. My D7 scanner has certain height recalibration settings but I'm not sure how to use them. I'm wondering if it's a calibration problem.

My current zero sensor setting is 52 centimeters from the fender. But the rear of the car doesn't rise to zero. It rises to 51 centimeters, and the sensor reading is -11. If I readjust the zero sensor setting to 51 centimeters, the rear of the car drops to 50 centimeters, and the sensor reading is -11 again. In other words, the rear never rises to zero. The distance from the fender to the front wheels is the same: 50 centimeters, leveled by torsion bars. The pressure in the front is 6.9, in the rear 6.2 (I installed spacers, but the sensor's performance hasn't changed), and the pressure in the hydraulic accumulator is 10.6.

 

[Magnaman]

My current zero sensor setting is 52 centimeters from the fender. But the rear of the car doesn't rise to zero. It rises to 51 centimeters, and the sensor reading is -11. If I readjust the zero sensor setting to 51 centimeters, the rear of the car drops to 50 centimeters, and the sensor reading is -11 again. In other words, the rear never rises to zero. The distance from the fender to the front wheels is the same: 50 centimeters, leveled by torsion bars. The pressure in the front is 6.9, in the rear 6.2 (I installed spacers, but the sensor's performance hasn't changed), and the pressure in the hydraulic accumulator is 10.6.

52 cm hub to rear fender using a tape measure is right on spec, I believe. So you're saying that your scanner should be reflecting zero and it isn't instead it says -11 like mine says -14, correct? So we have the same problem. Someone with more knowledge will have to try to explain. If you go under there and slide the sensor arm up towards the top of the slot will the car raise up higher? Have you tried unbolting the arm and moving it to try to get zero on your scanner?