It's not necessary to loosen control arms to adjust torsion bars. You do not need to remove the torsion bars either unless you need to re-index them if you have run out of thread on the adjusting bolt.
LX470 Torsion Bar Adjustment
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You spun the torsion bar 8 times and that side moved up 3/8"? You may want to measure again after some time. Roughly 1/8" per turn is normal.
Don't remove any torsion bars. That shouldn't be necessary unless you've got a really heavy rig and you're trying to do a sensor lift.
Good to know, thank you! So which procedure requires loosening and retightening the lower control arm bushings? Is that just for re-indexing the torsion bars?
Yes, I had read that same estimate, so when I measured the approximately 1/2" difference, I expected 4 turns would bring it very close to even. That only got me about half way there, so I put 4 more turns in it. Even then, it was still low, but I figure 1/8" is probably within my margin of error with a tape measure and trying to go off the hub center instead of the ground. As I said, I put 34 miles on it including both surface streets and highway, so I'm going to measure again today before reading out the neutral pressures. I also might check my fender-hub measurements against fender-ground measurements.
Thanks!
Measured again today, both from the hub centers and the ground. Saw as much as 1/8" to as little as no difference at all. I will probably recheck again after adjusting the neutral pressures, but I think it actually needed about 8 turns. Not sure why it wasn't leaning even more, unless my initial measurements somehow underestimated the lean.
Unfortunately, I'm having a hell of a time getting the driver for the Mini VCI cable to install on my Windows 10 laptop, despite trying multiple versions and manually extracting the .MSI file into my Program Files folder via the command prompt. So Techstream is pretty much useless until I can get it to realize that I have a cable plugged in. I really wish Toyota was required to just provide a free download of all this software so I wouldn't need to monkey around with some kludged together files from China.
Are you using the "Techstream in 5 minutes" virtual machine? If not, you should. Free, easy and compatible with both my cables.
I am looking to buy ARB tbars but there are 2 models; Old Man Emu by ARB 303002 and 303001. 303002 looks like suites diesel engines. Mine gas but didnt see details and Old Emu rear coils 2866. Not looking for lift. Wanted to check what are better suited parts.
I've crossleveled. And heights are all in spec 500 mm front both sides and 515 mm rear but to zero out my new height sensors my left height sensor is almost maxed out and my right height sensor is set to the minimum.. is that ok for the sensors to be that different ? Or did I miss a step somewhere in the torsion bar adjustment?
IndroCruise
SILVER Star
To start, let's assume that Sensors are in good condition and not suffering from internal wear and tear nor physical nor electrical degradation nor old age -- all of which eventually will happen in vehicles 14 to 22 years old.
Good that cross-level and physical heights have been set correctly. Height Control Sensors do not, and
cannot, alter front cross-level. Only the Torsion Bar adjusters can do this.
Now, connect Techstream, turn Ignition Key to "ON" but do not start engine -- do not want AHC to automatically self-level while doing Sensor adjustments.
With an eye on Techstream -- maybe use a USB to USB extension lead so screen can be seen while working at wheels -- and with Ignition Key "ON" but engine "OFF", adjust Height Control Sensors to near as possible to zero (+/- 0.2 inches) as seen on the Techstream reading.
Suggest use sliders, threaded heim bolt (front only) is good for fine adjustments, but is very fiddly.
If all that works, then the job is done.
If not, it may be time to examine
and test Height Control Sensors, physically and especially electrically per FSM and IH8MUD posts.
If Sensor readings are wildly different, the mixed signals (simple voltage signals from the potentiometers inside the Sensors) will result in the AHC Electronic Control Unit (ECU) selecting 'fail safe mode' in which either or both AHC and adaptive damping will not work -- rough ride, damping stuck in Step 8 of 16 Steps).
AS ALWAYS, WHEN DOING WORK LIKE THIS, POSITION VEHICLE STANDS UNDER CHASSIS RAILS TO PREVENT ANY ACCIDENTAL MOVEMENTS OF VEHICLE BODY ONTO HUMAN BODY.
Please post update when you can.
Thanks . That's pretty much what I had to do with heim and slider adjustment which is maximum out on one side and minimized out on other side.. I replace the left and rear sensor along with brackets with brand new from Amazon but the right side with brackets was not available so I only ordered the sensor itself and reused the old hardware.. I'll check again if something is bent out of place or perhaps the sensors from right and left are from a different manufacturer so the starting points are different.. (one for height and the other more for light leveling?)
Anyways I plugged in techstream and drove around with my wife reading out the numbers and everything seems to be matching to the road conditions as well a range of measurement appear appropriate. steering angle, front , left and rear heights seem to all correspond in a logical manner. At the end of the 30 min drive I measured the physical heights and all remain at 500 mm front both sides and 510 mm rear.
I think there is an input sensor active test I saw on the fsm which I will try and review the electrical connections however the test drive appears to show everything is working reasonably.
Perhaps one of my torsion bars has more fatigue that the other one?
Anyways I plugged in techstream and drove around with my wife reading out the numbers and everything seems to be matching to the road conditions as well a range of measurement appear appropriate. steering angle, front , left and rear heights seem to all correspond in a logical manner. At the end of the 30 min drive I measured the physical heights and all remain at 500 mm front both sides and 510 mm rear.
I think there is an input sensor active test I saw on the fsm which I will try and review the electrical connections however the test drive appears to show everything is working reasonably.
Perhaps one of my torsion bars has more fatigue that the other one?
IndroCruise
SILVER Star
The issue is about geometry rather than torsion bars, even if one TB is more tired than the other.
Suggest start from the ground and work upwards:
.. level ground,
.. tyres same diameter, equally worn, same pressures, meaning distances from ground to Left and Right fender lips are equal (as well as equal Left and Right hub-to-fender distances),
.. front and rear upper and lower control arms not damaged,
.. bushes not too worn nor damaged,
.. bearings correctly adjusted,
.. no reason to suspect chassis damage or twist.
If all is good, then it is difficult to imagine physical differences between Left and Right vehicle geometry with vehicle on a level surface.
As you already suspect, suspicion then falls on the sensors or linkages, new or not, or possibly on the electrical connectors. Either something is bent, or one electrical connector/harness is of significantly higher resistance than the other (poor connection or damage) or one sensor sends a different voltage to the ECU for the same brush position on the carbon track inside the sensor, or one sensor is electrically 'scratchy' and unreliable -- like a lousy volume control on an old radio. OEM Sensors should indicate a similar voltage at the same brush position on the carbon track and therefore at same swing angle of the linkage arm -- about 2.25 volts at mid-swing which the ECU requires at "N" height setting and when all physical heights are in order. Slight differences in manufacture mean that Sensors are unlikely to be exactly the same but should be close -- part of the reason for the adjusters is to overcome small differences.
It is easy to imagine differences between Sensors of different manufacture -- suggest keep to one brand rather than mixed brands around the vehicle to minimise this effect -- and maybe stick to AISIN (which is the OEM brand on Toyota/Lexus) or possibly Dorman -- although Dorman gets mixed reviews in IH8MUD posts.
Sensor problems will not always show as a DTC on Techstream, especially if the Sensor is still sort of working albeit poorly -- unsurprising given that Sensors are potentiometers which work at a range of voltages -- it probably takes an open circuit or a short circuit to throw a DTC.
The AHC Diagnostic section of the FSM gives Sensor test procedures. See
https://lc100e.github.io/manual/ then tabs Repair Manual > DIAGNOSTICS > Active Height Control Suspension & Skyhook TEMS > C1711 to arrive at Page DI-227).
There also are some practical methods using resistance rather than voltage suggested in this forum by @uHu and @PADDO.
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Thank you. I've got a logical roadmap of what needs to be done from what you said. Although everything seem to drives correctly even with techstream, something must be off since my height sensors had to be adjusted in such a polar opposite position.
Hi all, novice here. 06 LX with 199k and stock suspension with functioning AHC. My drivers rear is sitting 7/8” lower than passenger rear. Is it a horrible idea to adjust TBs without then checking AHC pressures? I don’t have Techstream.
Also I emailed with Slee Offroad yesterday (I’m taking my truck in for other things this week) and they explained that vehicle height couldn’t be balanced on AHC-equipped vehicles:
Adjusting the torsion bars on an AHC equipped vehicle will not effect the vehicle height as it is held up hydraulically by the shocks. You may have an electronic issue with a height sensor or a more complex issue with the hydraulic system.
From this thread this seems not to be true? I can in fact adjust TBs? Thanks in advance.
Also I emailed with Slee Offroad yesterday (I’m taking my truck in for other things this week) and they explained that vehicle height couldn’t be balanced on AHC-equipped vehicles:
Adjusting the torsion bars on an AHC equipped vehicle will not effect the vehicle height as it is held up hydraulically by the shocks. You may have an electronic issue with a height sensor or a more complex issue with the hydraulic system.
From this thread this seems not to be true? I can in fact adjust TBs? Thanks in advance.
BullElk
SILVER Star
You can turn the TBs but it will not raise the front of an AHC LX.
IndroCruise
SILVER Star
The statement by Slee is consistent with the operation of the AHC system and is consistent with explanations earlier in this thread and in many other IH8MUD threads on similar topics.
Some long-winded clarification may help ….
- the AHC system on LX470 (and LC100 where fitted) is a “two channel system” – Front and Rear – it is not a “four channel system” and does not raise/lower each of the four wheels independently,
- Rear height is controlled by the AHC Electronic Control Unit (ECU) receiving input from the single Rear Height Control Sensor, mounted on the cross-member forward of the rear differential and linked to the LHS Rear Upper Control Arm,
- Front height is controlled by the ECU averaging the input received from the two Front Height Control Sensors, mounted respectively in the LHS Front wheel arch and the RHS Front wheel arch and linked to the respective Front Upper Control Arm,
- Assuming that the Height Control Sensors AND their connectors AND harnesses are in good condition AND all Sensors are correctly adjusted (and that’s a lot of assumptions on 14 to 23 year old vehicles!), then when in operation with engine running the ECU will cause automatic self-adjustment of front and rear heights, based on inputs from the Height Control Sensors and on the selection of “LO” or “N” or “HI” at the AHC switch on the centre console,
- To self-adjust height upwards, the ECU causes the AHC Pump to run -- this adds pressure and causes fluid to flow to the ‘shock absorbers’ (which really are only hydraulic struts in an AHC vehicle) and raises the Front and/or Rear of the vehicle until the ECU receives the correct signals from the Height Control Sensors for the height selected on the console switch,
- To self-adjust height downwards, the ECU causes the Levelling Valves in the Control Valve Assembly to open – this releases pressure and allows fluid to flow from the ‘shock absorbers’ back to the AHC Tank and lowers the Front and/or Rear of the vehicle until the ECU receives the correct signals from the Height Control Sensors for the height selected on the console switch.
What does all this have to do with the Front torsion bars?
The front torsion bars (and rear coil springs) carry shares of the vehicle weight which are not carried by the AHC system.
The AHC system has no way of sensing the condition or adjustment of the torsion bars (nor the condition of the rear coil springs) – these must be observed manually by the owner or mechanic.
It is important that the Front Left and Front Right torsion bars carry equal shares of the vehicle weight. This is checked or adjusted by a process called ‘cross-levelling’. The term ‘cross-levelling’ is a bit confusing because it has nothing to do with setting the ‘ride height’ of the vehicle which is controlled only by inputs to the ECU from the Height Control Sensors and by the adjustment of these Sensors.
To be clear, 'ride height' is not adjusted by the torsion bar adjusters on an AHC-equipped vehicle.
The purpose of ‘cross-levelling’ is to equalise the loads carried by the two front torsion bars.
When the vehicle is stationary (and when the steering is straight ahead), the Front Left and Front Right parts of the AHC system are connected hydraulically because the Gate Valves in the Control Valve Assembly are open in this condition.
This means that the AHC pressures on Left Front and Right Front are equal.
In this condition, and assuming (more assumptions!) that all mechanical suspension components are in good condition, then the only thing which can cause differences in Front Right and Front Left heights is the torsion bars.
When the Front Right and Front Left heights are equal (best measured from hub centre vertically to the fender lip above),
- the torsion bars are equally loaded, and,
- front side-to-side lean is eliminated (within FSM-specified tolerance – see attachment).
Theoretically (assuming – that word again -- that the AHC system is healthy), it should not matter when the cross-levelling measurement is done when the vehicle is stationary because of the hydraulic connection mentioned above – but to avoid confusion it is best done when the engine and AHC are “OFF”.
Certainly, for safety and because the FSM says so, cross-levelling adjustment should be done when the engine is “OFF”.
In a case where the reported driver’s side rear is low by 7/8 inch, then the diagonally opposite passenger side front should appear high compared to the driver’s side front.
This is because the corresponding points of the chassis should all be in the same plane, forming a stiff rectangle.
If such corresponding differences are not observed then possible causes need to be explored – such as
- not measuring on a level surface,
- unequal distribution of loads and/or weight of fittings on the vehicle,
- different tyres or unequally worn tyres or unequal tyre pressures,
- worn or damaged suspension or axle components, bearings or bushes,
- twisted chassis as a result of a hard life or accidents.
The torsion bar adjusters have two purposes on an AHC-equipped LX470 or LC100. These are:
- to achieve ‘cross-levelling’ – easy, requires only a tape measure to check hub-to-fender distances, and,
- to adjust Front AHC pressures into the FSM-specified range – also easy, but requires Techstream or some other scanner which can read the AHC Electronic Control Unit.
How-To: TechStream In 5 Minutes - https://forum.ih8mud.com/threads/how-to-techstream-in-5-minutes.1034923/#post-11416736
If not already seen, the General Description of the AHC system and TEMS system is a worthwhile read. See
LC100 Workshop Manual - https://lc100e.github.io/
then follow these tabs at the Index Panel
New Car Features > CHASSIS > Suspension > Active Height Control Suspension and Skyhook TEMS
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What happens if I tighten both tbars two or three turns?Wouldn’t this simply lower the pressures on the front and raise the pressure on the rear?My ride just seems a little harsher than it should be(in any suspension setting).If worse comes to worse,couldn’t I put it back where it was.No,I don’t have access to tech stream…
I tightened my Torsion Bars 3 turns CW per the pressures in TechStream.
Drove it for 5 years and a couple months ago I backed out 1.5 turns CCW because I thought the ride was too harsh.
Not sure if it made a significant improvement.
Might go back to the way it was by backing out another 1.5 turns CCW and see.
Drove it for 5 years and a couple months ago I backed out 1.5 turns CCW because I thought the ride was too harsh.
Not sure if it made a significant improvement.
Might go back to the way it was by backing out another 1.5 turns CCW and see.
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