Torsion Bar Adjustment - LX470 AHC

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.

Joined
Apr 13, 2014
Threads
46
Messages
234
First pic, I am lying underneath the driver side, looking towards the front of the vehicle. Second pic, I am still lying under the driver side, but looking towards the back of the vehicle.

1. I have highlighted three bolts i.e. #1, #2, and #3. Which is the one that cranks the torsion bar?

2. My front driver side needs to be raised to cross-level. Whichever bolt it is above, should i turn it in Orange arrow or Pink arrow direction to raise the front driver side?



1717337599278.png




1717337636282.png
 
On techstream here are my BEFORE readings:

front LEFT was -0.3
Front RIGHT -0.0
FF pressure: 7.9
RR pressure 7.4

Cranked the LEFT (driver) side TB Bolt #1, two turns CLOCKwise (orange arrow). Here are the readings afterwards:

front LEFT -0.2
Front RIGHT —0.1
FF pressure: 7.7
RR pressure 7.4

So it looks like I’m almost there with cross leveling.

The question is now to reduce the front pressure further do I need to crank the torsion bar bolt clockwise by equal amounts in the SAME CLOCKwise direction on both the left and right side…. Because we are now not cross leveling and want the torsion bars on both sides to take equal higher amount of pressures in order for the AHC to have reduced pressure?
 
In other words:

Lying underneath the vehicle on Left/Driver side and looking up, turning the Bolt 1 CLOCKWISE (Orange arrow) will "raise" the vehicle height on that side. I have completed that.

Now on the passenger side, lying under and looking up at the Bolt, do we turn it CLOCKWISE or ANTI-CLOCKWISE to "raise" the height?

thanks.
 
Remember on a AHC vehicles torsion adjustment will NOT change the height. Torsion adj. only changes the pressure.
To change height you adj. the heim joint located by the upper control arm.
 
Yep, I am on the same page. That’s why I put the word raise in quotes because it isn’t truly raising the height but merely contributing more to hold the weight of the vehicle to reduce pressure on AHC.
 
Keep in mind the heights on the sensors left and right are completely meaningless for cross leveling. You want to get the car level, then you can mess with the sensors individually until they read 0.0 each.

To measure the heights for cross leveling you need to know the actual height of the physical car. Typically that's measured at the hub to fender, but you can also measure parts of the suspension, per the Toyota manual.
 
After all the turning when I measure my front right and left the right side is about 1/4" higher. At this point should I work with the height sensor? If yes, I understand that we need to:

"Shorten heim joint to raise height... lengthen it to lower the height"

Two questions:

1. To adjust this heim joint, can the vehicle be on the ground .... or that wheel / front two wheels / all four wheels have to be off the ground?

2. Can any one point to a video on how to adjust this heim joint? I've been looking around but can't find a good one.
 
No reason to lift vehicle to adjust heim joint. I actually lift AHC to H to access heim joint easier.

Use 10mm to take off nut at the adjustment slide, top of heim joint. That will free up the entire joint to work with. The heim joint threads from both ends with lock nuts on each end to hold each end tight. Simply loosen the lock nuts, turn each end in the direction to move them closer together, tighten lock nuts, Install top end back into the adjustment slide as high as it will go in slide. Tighten 10mm nut.

That will maximize your height sensor adjustment. The closer you move each end of the heim joint together and the higher you slide it up in the final slide adjustment.....the higher vehicle will be.

If you go this route you need to align tires or you will definitely get one edge of tire wearing more that the other.
 
After all the turning when I measure my front right and left the right side is about 1/4" higher. At this point should I work with the height sensor?
No.

Cross levelling adjustments cannot be done with Height Control Sensors.

The LC100/LX470 AHC system is a two-channel system -- Front and Rear only. It is not a four-channel system as would be required to adjust heights at each of the four wheels individually.

For height control, the ECU will reduce the voltage signals from the two Front Height Control Sensors to one value and then using these Sensors and the AHC Pump and the Levelling Valves, will attempt to find a height position at N or at LO or HI -- whatever is selected at the console switch -- that best matches the programmed value at N or LO or HI (for example, ~2.25 volts at N -- which corresponds to ~zero inches or millimetres at N on Techstream or other scanner).

If cross-levelling is attempted with Height Control Sensors the guaranteed result will be confusion and frustration -- and possibly end with the voltage signals from the Height Control Sensors being so different that ECU cannot resolve them and adopts the "fail safe function" which prohibits height changes by AHC and prohibits variable damping by TEMS.

Instead, always start any AHC adjustments, or checks, by cross-levelling the Front on level ground like a garage floor (not in the street), with engine OFF, using a tape-measure and the torsion bar adjusters to equalise Right and Left hub-to-fender measurements.

Measure this cross-level at N height. It can be easier to turn the torsion bar adjusters at HI height -- no problem with that -- but always check the final results at N height. Don't worry about the actual tape-measurements at this stage -- just make Left and Right equal -- FSM says within 10 millimetres = 0.39 inches but try to do better. [NOTE: If there is wear and tear or damage in the Front OR Rear suspension, this can be more difficult than it seems].

With cross-level correct, 'ride height' is set with the Height Control Sensors as described by @BullElk in Post #11 this thread.

Within the range of adjustment of the Height Control Sensors, choose your preferred 'ride height' at N, increasing it if desired -- the so-called 'sensor lift' -- just be careful that (1) enough droop remains when the suspension is fully extended, and (2) wheel alignment is checked and adjusted if necessary.

The ECU is permanently programmed to use the AHC Pump and the Levelling Valves and the Height Control Sensors to seek the correct voltage signals that match N height when N is selected at the console switch (means a Sensor signal of ~2.25 volts and showing ~zero inches or millimetres on Techstream). These ECU settings CANNOT be changed. Likewise there are permanently programmed non-changeable ECU settings for LO and HI heights.

What CAN be changed is the position of the Upper Control Arm relative to the potentiometer arm inside the Height Control Sensor. This is what is being done by moving the Height Control Sensor adjusters.

Whatever is done with Height Control Sensor adjusters, when N is selected at the console switch while the engine and AHC system is operating, the ECU always will cause the 'ride height' to change until it finds a Sensor signal of ~2.25 volts and shows ~zero inches or millimetres on Techstream -- which is correct for N height. When LO or HI is selected at the console switch, the ECU will cause a response which matches the permanently programmed settings for LO or HI height respectively. This fundamentally is how the AHC system works -- UNLESS there are adjustment faults or faults in the Sensor or the connector or the circuit/harness (or in the ECU -- very rare), but all of those faults are another story ....

AHC Front Height Control Sensors.jpg


AHC Height Control Sensor Description.jpg


LC100 Sensor Voltages.jpg
 

Attachments

Last edited:
On techstream here are my BEFORE readings:

front LEFT was -0.3
Front RIGHT -0.0
FF pressure: 7.9
RR pressure 7.4

Cranked the LEFT (driver) side TB Bolt #1, two turns CLOCKwise (orange arrow). Here are the readings afterwards:

front LEFT -0.2
Front RIGHT —0.1
FF pressure: 7.7
RR pressure 7.4

So it looks like I’m almost there with cross leveling.

The question is now to reduce the front pressure further do I need to crank the torsion bar bolt clockwise by equal amounts in the SAME CLOCKwise direction on both the left and right side…. Because we are now not cross leveling and want the torsion bars on both sides to take equal higher amount of pressures in order for the AHC to have reduced pressure?

Hi, I was reading this thread and I'm trying to get my head around pressures on my 2006 Sahara with AHC. I can anyone read the tea leaves for me? The truck will only go into low sometimes. In this case I could not lower it.
MyAHC.jpg
 
Last edited:
Hi, I was reading this thread and I'm trying to get my head around pressures on my 2006 Sahara with AHC. I can anyone read the tea leaves for me? The truck will only go into low sometimes. In this case I could not lower it. View attachment 3799484
This thread your in, may confuse you. As OP didn't have a good understanding of AHC.

Here's a thread and video that should help you much more:
 
Concur with 2001LC.
But to give you a flying start, with the difference between the readings from the two front sensors, the AHC will not behave. If the car is level left-right, you need to figure out the height sensors. Also, the pressure readings will be valuable when moving from L to H, and when the physical heights are within specs.
 
This thread your in, may confuse you. As OP didn't have a good understanding of AHC.

Here's a thread and video that should help you much more:
Hi Paul,

Thx for the guidance. I'm now confident that it's all AHC is working as it should, although no sooner did I sort that another issue arose. This time it's complaining about the master cyl pressure sensor.

I am now reading the threads but this seems to me not to be a brake accumulator or motor issue and there is a check engine night but no brake warning lights on the dash see attached images. Should I raise another thread or could I PM you for advise. Thx.
This thread your in, may confuse you. As OP didn't have a good understanding of AHC.

Here's a thread and video that should help you much more:

PXL_20250113_111109072.jpg


1737268075818200956247396807493.jpg
 
Hi Paul,

Thx for the guidance. I'm now confident that it's all AHC is working as it should, although no sooner did I sort that another issue arose. This time it's complaining about the master cyl pressure sensor.

I am now reading the threads but this seems to me not to be a brake accumulator or motor issue and there is a check engine night but no brake warning lights on the dash see attached images. Should I raise another thread or could I PM you for advise. Thx.


View attachment 3819188

View attachment 3819189
Working in, Public thread. is best.
 

Users who are viewing this thread

Back
Top Bottom