OK Guys (and thanks again
@IndroCruise )
I still feels like I have no suspension at all. I went through the overall AHC/Neutral Pressure process this afternoon. Here is what found out, but I didn't do any fine tuning of the neutral pressures with Torsion bars.
1. Heights are close
-FL 19 7/8
-FR 19 3/4
-LR 20.5
-RR 20.5
Neutral to Low - 12 seconds
Low to Neutral - 17 seconds
Graduations L -> H are 10+ (even with what I believe to be a globe leaking nitro)
The height sensor readings appear to me to problematic, but I don't now how to interpret it. According to Techstream there are no error codes. how do I get negative readings on all sensors? I thought the FL and FR should balance at zero. I had all new links/bushings/stops, etc installed in the front and I recently had new OEM springs installed in the rear. Perhaps the local dude that did the installations for me tweaked the sensors or linkage somehow. not sure if a tweaked sensor would cause these readings or the rough ride.
I plan to do the 1-16 actuator test tomorrow, but any help identifying where I should be investigating is much appreciated. I don’t think the slightly high rear neutral pressures are my problem. Thanks!!
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Deepest sympathy for these frustrations!! My vehicle has some unresolved problems with some similarities and some differences to your case. I will write up my situation in the next few days and post a separate story, so as not to distract others from replying to your own post above.
Meanwhile, here are a few thoughts on your readout:
At first blush, the basic readings appear ‘healthy’: presume ‘cross-levelling’ is OK, correct-looking physically measured hub-to-fender operating heights, not unusual AHC pressures, and the HI/LO 10+ graduations look good!
However …….
The top three lines showing Height Sensor positions at the end of the LO to N movement are strange. The differences between each Sensor are not huge but it is unusual that they are ALL not closer to zero and are significantly below zero. This is a particular concern if this is observed consistently with repeated measurements when moving from LO to N.
It does raise questions as to whether the lift from LO to N actually has been completed by the system, and if not, what is preventing the system from doing so?
The design is such the system is meant to find the ‘null’ point at which the Height Control Sensors give a close-to-zero reading when the vehicle has raised to N -- for any N height chosen by the person who last manually adjusted the Height Control Sensor positions at N.
Different effects can be tricky to diagnose, because some obscure faults may not result in in a Diagnostic Trouble Code (DTC). These could include situations such as mechanical issues in the suspension, or, weaknesses such as a continuing but not yet fatal decline in AHC pump performance, or, a developing blockage impeding pressure build-up and flow of AHC fluid at the pump or elsewhere, or, improper operation of the solenoid valve on the large Height Control Accumulator, or, faulty valve operation in the Control Valve Assembly, etc.
Note that there is no ‘brain-power’ or control loop inside in the Height Control Sensors. They are mere sensors -- simple but robust potentiometers in which a different vehicle height causes the tiny internal brushes to be at a different position on a carbon trace, in turn giving a different resistance and different output voltage, interpreted as a relative height by the AHC Electronic Control Unit.
Only physical adjustment of this Sensor position is possible, and this must result in a matching actual change in the hub-to-fender measurement. I am unaware of any way that the Sensor readings can be “zero’d” or adjusted in Techstream. Other IH8MUD Members may know different.
It would be tricky. This is because heights and pressures are interdependent. Or more precisely, the torsion bar deflection depends on the load carried (like a spring) and load not carried by the torsion bar must be carried by the relevant AHC Actuator and Gas Chamber (‘globe’).
The only means of load transfer between torsion bar and AHC is via manual adjustment of the torsion bar adjuster. The AHC Electronic Control Unit has no connection with the torsion bars nor control over them. The ECU can read the AHC Pressure signal and the Height Control Sensor signal and respond to those (among the multiple other signals it receives).
The ECU cannot itself optimise torsion bar load, AHC load and vehicle height a.k.a. hub-to-fender measurements.
So questions arise from your readings:
What are the hub-to-fender measurements
immediately after the N >> LO >> N height movements and AHC pressure readings?
Are the hub-to-fender measurements at this point the same as those given in the above post, or, are they now lower, giving rise to the lower sensor readings?
If lower, then the AHC pressures relate to those lower measurements and the AHC pressures would be higher at the higher measurements (and ride comfort would be different, and likely rougher).
Do the hub-to-fender measurements change after you have driven around the block and the suspension has settled?
If so, how can the AHC pressures be determined at these higher hub-to-fender measurements?
At the moment, I cannot offer a clever answer to these questions but only report that currently I am dealing with a very similar problem on my own vehicle …..
Meanwhile, I have pasted a couple of links below which highlight some different problems and ideas – they may or may not be relevant and you may have seen them previously.
I also notice that your steering angle seems quite a long way from zero. It is unlikely ever to be perfect but if this is the repeatable reading with the front wheels truly straight ahead, then it suggests that toe-in or some other aspect of wheel alignment may have been achieved in unequal ways on Right and Left wheel alignment adjusters, or that there is something worn or incorrect in the suspension or steering mechanicals, or that there is something wrong with the Steering Angle Sensor.
The relevance is that when the ECU thinks that the wheels are straight ahead, the ECU directs the front gate valves in the Gate Valve Assembly to be open, which causes Right and Left front AHC pressures to be equalised.
When the angle exceeds 36 degrees (check FSM), the relevant gate valve closes and Left and Right pressures cannot equalise. This is how some variable roll resistance is included in the AHC/TEMS system in addition to the mechanical sway bars.
So I am wondering whether your -51.75 degrees steering angle at ‘straight ahead’ actually means that there is some pressure "locked in" by the gate valve affecting one side and distorting your efforts to ‘cross level’ correctly and preventing equalised front torsion bar loadings?
Hopefully, other IH8MUD Members will have more to offer on all of the above matters?
Several easy and practical indicators which I use are suggested below:
These suggestions may give you further information about how the system is operating, or, whether it is not operating due to a fault condition or ‘fail safe mode’ in the AHC/TEMS systems, or, whether suspension/steering mechanical issues should be explored:
- The Height Control obviously works because you can lower and raise the vehicle, take pressure readings and do the HI/LO volume test. So that much is a positive. It leaves us wondering about the adaptive variable suspension component of TEMS,
- Suggest drive over a set course a few times, preferably with little traffic, so that you can concentrate on the vehicle, then on each go-round use a different setting on the four-position Comfort Switch on the console, then sense by the seat-of-the-pants whether there are differing degrees of ‘felt comfort’ at each setting. It seems that you already have done this and the harsh ride is one 'symptom' you have experienced. Is the experience the same at all Comfort Switch settings?
- Suggest hook-up Techstream so that you can safely look at the screen while driving, or better still, have someone else drive while you look at Techstream screen,
- On the screen, you should be able to see all of the Height Sensors responding in almost real time to the ground over which you are passing. If any of them are not moving or seem to be moving erratically and inconsistently with ground conditions, then that is a worry and warrants a closer look at the relevant Sensor(s),
- Now suggest look at the following lines on the Techstream readout on the screen of your laptop or device while the vehicle is still on the move:
- “Front Wheel Step” and “Rear Wheel Step”: These should indicate whether the ECU is signalling the step motors in the Damping Force Actuators to operate in the appropriate range for the chosen setting on Comfort Switch on the console. When the vehicle is stationary, both Front and Rear readings should show position 8 (of 16 positions). In at least one of the ‘fail safe modes’ the system may remain in this position 8 even when the vehicle moves. If so, that is a 'symptom' worth knowing. Suggest take some screenshots to look at later,
- Suggest vary the Comfort Switch through each of the four positions while the vehicle is moving and study the responses. If the system is working, at ‘Comfort’ (softest damping) you should see a wide range, say 1 to 9, at ‘Normal’ it is more like 3 to 12, at Sport1 maybe 8 to 12, at Sport2 (hardest damping) maybe 12 to 14. (These are approximate numbers from my memory only). In most Comfort Switch positions, large changes in damping also may be seen during hard turns, or heavy stops, or heavy accelerations. This gives some evidence of what the system is doing or not doing. Again, suggest take some screenshots to look at later,
- While making the observations in the above para, also while still on the move, look at the lines “Damping Force Switch 1” and “Damping Switch 2”. These refer to the instructions given to “Soft Damping Force Valve” and the “Hard Damping Force Valve” found inside each Damping Force Control Actuator. This is about HOW the ECU controls the ‘damping map’ to be used according to the choice of Comfort Switch position on the console. As I understand it, these lines in the readout indicate the signal sent by the ECU to the Actuators rather than what the Actuator actually does! A discrepancy between the ECU and the Actuator should result in a DTC,
- As you move the Comfort Switch on the console through its four positions, you should see the four different combinations of switching for each of Switch positions, ending with both switches OFF at the Sport2, the hardest setting. I have not tried it but I also surmise that the switching may change in a hard turn, driven by the Steering Angle Sensor? Again, suggest collect data with screenshots. (Note that there is no ‘brain power’ in the Damping Force Control Actuators – the instructions come from the ECU and control movements of the step motors and solenoid operation of the internal valves),
- It is worth revisiting the “Damping Force Controlling Condition Check” (also known as the ‘16 Step Test’) , and, “Height Control Operation Test” (also known as the ‘Active Test’) to test properly the functionality of these parts of the AHC/TEMS system, before moving on to other issues.
- The FSM reference is: https://lc100e.github.io/manual/,
- Follow index tabs to Repair Manual > DIAGNOSTICS > ACTIVE HEIGHT CONTROL SUSPENSION & SKYHOOK TEMS > PRE-CHECK,
- Then go to Item 4 on page DI-213 and Item 5 on page DI-214.
- Note that bridging terminals E1 to Ts at DLC1 in the engine bay with an unbent paperclip is the same as, but much more comfortable than dealing with the connections at DLC3 mentioned in these FSM references, while upside down under the dashboard!
- Make the connections with the engine and ignition OFF, then start the engine. Remember to turn OFF the engine and then remove the bridge when finished.
- See also this succinct summary from @PADDO: AHC with harsh ride .
- As @PADDO mentions, the vehicle can be driven in this condition and the Techstream screen readouts and vehicle response can be observed on the road at each of the 16 actuator switch settings one-by-one – but CAREFULLY because in this condition the adaptive variable suspension, ABS and A-TRC are all OFF with multiple dashboard warning lights flashing. These systems will automatically restore when the engine/ignition is switched OFF, bridge removed and the engine re-started.
- Finally, here is a quick on-vehicle Height Control Sensor test provided by @uHu: 2007 LC “VX” -- first reply by @uHu, and, 2007 LC “VX” -- second reply by @uHu ,
- By the way, it is not a hard job to remove the Sensors from the vehicle – two accessible bolts to the chassis, one linkage bolt to a sliding adjuster, a couple of cable clips, and one fiddly electrical connector to unlock and release in each case.
- Make access easy at the front by raising to HI height and turning the front wheel to full lock,
- At the rear, either remove LHS rear wheel or get under the car,
- NEVER get under the vehicle when dealing with any part of the AHC system without putting car stands in place under the chassis rails to ensure that the car is positively and physically prevented from lowering itself onto a person -- it can happen, has happened but it should never be allowed to happen!
Strong recommendation: Take photos before removal of the Height Control Sensors so that you have clear record of your starting point. Once removed, inspecting sensor internals and testing is very straightforward and makes any replacement decision easy. Take more photographs. Record measurements for later reference. Along the way, also test the harness circuit for supply voltage and continuity.
Two posts with more explanation – with pictures
AHC, Actual Height, Pressures - LC100
This next post includes comments and attachments on more diagnostic approaches and material:
2007 LC “VX” -- see notes in reply by
@IndroCruise.
Last reference: Probably this document has been seen previously but is recommended that it be printed in hardcopy and re-read every time when dealing with AHC/TEMS problems. It provides a good well-illustrated 20-page descriptive reminder of how all the parts of this 25-year old, robust-if-well-cared-for technology can still work together to produce a great ride:
The FSM reference is: https://lc100e.github.io/manual/,
Follow index tabs from the top to
New Car Features > CHASSIS > Suspension > Active Height Control & Skyhook TEMS
More later after I do some more work on my vehicle!
I did read (after my failure) that there is a risk of rear height sensor damage when replacing coils or adding spacers, but I didn't find information on what kind of damage or how to check for it. Any thoughts on what I damaged or what I need to look for in TechStream when I get it up again?
