Diagnosing Violent-Jerking Steering Issue (VGRS)

[2001LC]

Probably not really relevant to the issue that you’re chasing, but I believe the 3 AHC DTC can be made to go away, by unplugging the bottom two connectors on the AHC ECU. The 4th body DTC appears to be a “rain sensor” (even less relevant to your issue).

THX, good to know! Although both AHC & VGRS get sensory input from many of same sensors. We don't think either, that those DTC from AHC. Has anything to do with current steering issue. I was just making note, they've been current for much longer than current issue, as I showed no VGRS DTC.

The lack of VRGS DTC, perhaps a clue!

 

[Eyedaho]

I found this VGRS explanation online. It looks like there's a locking mechanism to stop the VGRS actuator from rotating the strain wave gear in the event of a system failure. If you unplugged the VGRS ECU and still had the high speed wobble issue then it seems that this solenoid should have not been actuated and the VGRS should have been overridden? You might be able to confirm by finding the lock solenoid and unplugging power to it and seeing if the issue persists. If it does, it seems that either the lock mechanism has failed or the issue is not with the VGRS, since VGRS should not be operating with the lock solenoid not having voltage applied (failsafe).

 

[2001LC]

I found this VGRS explanation online. It looks like there's a locking mechanism to stop the VGRS actuator from rotating the strain wave gear in the event of a system failure. If you unplugged the VGRS ECU and still had the high speed wobble issue then it seems that this solenoid should have not been actuated and the VGRS should have been overridden? You might be able to confirm by finding the lock solenoid and unplugging power to it and seeing if the issue persists. If it does, it seems that either the lock mechanism has failed or the issue is not with the VGRS, since VGRS should not be operating with the lock solenoid not having voltage applied (failsafe).

I've also read the same. System is locked (inactive) until power (12V) added to it activating solenoid.
I disconnect only wire housing block from actuator to ECU, which is also power feed. Which I assume solenoid in actuator. No change (violent jerking). No DTC or VGRS light (VGRS light does work, during key on self test). Front-end checks-out, as all good and tight.

But as stated early; diagnostic have not yet been done. Just test drove, actuator connected then disconnected. We found speed made no difference. It really seems to be and issue were cold, steering okay. But once driven a few minutes, steering issues comes back. The more turns the faster it returns. HWY speed is not a factor, as we found at slow speeds never getting over 35 MPH, it starts happening after a few turns.

More than anything, we want to know the why. The why, should always be determined. Which in this case will weigh heavy on whether to repair or convert to non VGRS. If this was a stock rig, with stock VGRS R&P. I'd have much less concerns.

We've concerns just fixing which is likely replace the actuator, that condition returns, if we don't know the why. If, and this is a big "IF", it is due to an LC R&P (NON VGRS) installed 2 years ago. Then we need to consider cost of new R&P in addition or convert to LC steering.

Here's what we do know, at this time:
Off-road built rig. Wherein AHC system was also removed.
New OEM LC rack & pinion installed, which was none VGRS R&P.
Steering at slow speed harder, mile one after the non VGRS R&P installed.
This failure was ~2 years after R&P installed, and a few hundred miles after new tires and alignment. (New tires, would add to resistance in steering system)

So why was steering hard after non VGRS R&P installed?
Is the gearing within R&P VGRS & NON VGRS, different between the two? I have long, assume so. But have yet to confirm???
Does this difference, put more pressure/resistance on VGRS actuator?
If it does put additional resistance on Actuator, does this lead to premature failure?

The other side of the coin:
At the time non VGRS R&P installed, a malfunction was present. Either before or just after install?
Was this from not properly calibrating before or after, or just a warn-out of defective part (Lexus changed PN, the next year and 2 more times subsequently)?
Was/is hard steering a sign of failure?
Was system in fail safe mode and driven so all these years, and just now finally failed?

 

[pili]

I'm sure @2001LC will follow up with a more technical post at some point (Paul is still trying to understand the root issue as I understand it), but he replaced the VGRS actuator and it appears to have fixed the issue. Just wanted to follow up.

 

[2001LC]

I'm sure @2001LC will follow up with a more technical post at some point (Paul is still trying to understand the root issue as I understand it), but he replaced the VGRS actuator and it appears to have fixed the issue. Just wanted to follow up.

Replacing VGRS actuator does seem to have fixed the very violent jerking to the right issue. But limited mileage at this point, so jury is still out. But we are 98% sure, replacing actuator fixed the issue.

But Surprisingly, Alex reported the steering much easier now. He's words "Like night and Day" better. Better than has be since the non VGRS LC rack & pinion (R&P) installed, 2 years ago.

So why did steering become harder in slow speed, at time R&P installed 2 years age? Why did actuator fail? I suspect more than one factor. But highly suspect a failure to fully calibrate, was a big factor.

Bottom line we do not know why hard steering started 2 yrs ago or why the VGRS actuator failed, but I can offer up some clues:

I know the shop that replaced the R&P 2 years ago. I can't say all in that shop, use air hammer to pop off intermediate shaft No 2 from the R&P, but most do. It's actual is a common practice. TSB for snap ring recall clearly states, do not hammer in direction of actuator. Which the air hammer technique does.

There is a calibration procedure in the TSB & FSM, that needs following. It may not have been. It's a longer procedure, than most know/understand.

Before R&P install:

The Seal at firewall is required to be replaced, when snap ring recall service done. It was not! In fact it was damaged and allowing air, dust & moisture into actuator boot, which we do not want.

Vehicle shows signs of front end damage. Possible impact, did some unseen actuator damage.

 

[2001LC]

We've still have something wrong, DARN!

New actuator correct 2 things:

• Stopped the very violet jerking to the right repeatedly, with steering wheel disconnect from steering rack.
• The hard steering at slow speed has not come back, while VGRS connect (powered).

But DARN!

• We did get a minor jerk feel in steering wheel, after a few days of driving. Which takes about 30 minutes of driving each time, before event. Similar to what we first had, but not hard right or violent, nor the scary feel of steering disconnect. This was with VGRS active or disconnected.

Hard steering appears to have not been from a LC rack in a VGRS LX:

We disconnected new VGRS actuator, and found steering hard at slow speeds. Just like before actuator replaced, and had been for past 2 years (since LC rack installed). With new actuator active, steering is easier (normal). This indicates old actuator, had been in fail-safe for 2 yrs. Or going into fail-safe most all times, without any dash lights or DTC (codes).

Now what:

We're going to inspect front end again. i.e rack, ball joints, etc. Then have Lexus Dealership have a look. Need more eye balls on this. Many Lexus models have VGRS, perhaps they've seen the issue before.

Unless a fluke and new actuator bad. We must have some other issue, either mechanical or pressure related. Which may have contributed to damaging old actuator.

Nothing I've seen before, that for sure.

It maybe, the very violent issue cause another/Laurent problem. We know it knocked out the toe.
Could be current feel/issue, root of issues.

 

[2001LC]

I wouldn't call it a vibration, more of a shake or wobble. I will pop the dust caps off to check the hubs to check the c-clips Here's a video of what it looks like. steering wobble

This looks to be a steering system issue, but entire front end needs to be inspected.

@cruisermaine I just review your video. This is similar to @pili issue. Although his at first was a very violent jerk to right, than release feel as if steering wheel disconnects (no control) from rack, than repeat rapidly. Now @pili 's is more like what you have, but not as pronounced. We now know his actuator had not be engaged (at all or most of the time) for past 2 years.

You may just need a proper calibration. "Current thinking" is, disconnecting the VGRS actuator should stop the "wobble", if only a calibration issue.

Check to see if your VGRS is engaging. Note, VGRS ECU will shut down actuator without VGRS light on, under certain condition as a fail safe. One of which is high temperature of actuator.
First when cold, than as the event happens after warm up drive stop and check again. Do this test a few times.
Start engine and let ideal, while in park, turn your steering wheel all the way toward one side until it stops (lock), than turn all the way to other direction (lock).
Lock to lock, VGRS engaged - 2.4 turns.
Lock to lock, VGRS not engaged - 3 plus turns.

Some ??
Any modification to your 06LX, form factory configuration?
Is the factory rack & pinion still in or is it a replacement (which rack & pinion do you have)?
Has steering snap ring recall been done?
Is slow speed steering, a bit hard, cumbersome or very easy, compared to other 03-up LX?
What fluid is in PS reservoir, how old and what is the level currently?
Is the steering rack, its lines, pump leak or any been replaced?

@cruisermaine I posted some post from your "wobble" thread here. As we may be dealing with a same or similar issues.

Steering wheel wobble - transfer case or actuator motor failure?

forum.ih8mud.com

 

[mystican]

@cruisermaine I post some post from your "wobble" thread here. As we may be dealing with a same or similar issues.

Steering wheel wobble - transfer case or actuator motor failure?

forum.ih8mud.com

any update on this issue?...I am looking at replacing my Lexus VGRS steering rack with a non VGRS Toyota rack...

 

[2001LC]

Nope, and there will not be any more updates on OP (this) vehicle.

Decision was made, to not fix the issues. It was no longer the volent jerking, more a minor twitch. Still, not something that felt safe to drive with fear it could get worst.

It may have not been mentioned earlier. The Vehicle had been in at least one front end accident. We've learned in talking with a few Lexus Dealership. The only VGRS actuators they've ever replaced, were accident related. BTW: VGRS is not just in LX, it in many Lexus models.