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Help, My Lexus Is A Dragster!


Mike Floutier
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Hi all,

My LS430 has now done 225,000 miles and I have a fairly serious problem - as you can see from the attached photo.

I had been concerned about general stability recently when, the other night, the "height hi" warning, plus red triangle came on, but went out pretty soon. The next day it stayed on for an hour.

The front is not affected (has always been fairly high) but the back is now up at dragster height - see pic - same at both sides.

I should say that I have read everything on the UK and US sites along with the Landcruiser stories and the LS430 workshop manual.

When I switch off the the engine the rear height eventually goes down a way, but not as low as normal. Starting the engine while stationary does not cause it to rise, but as soon as I drive off it goes right up.

The warning rarely comes on now (inspite of the problem persisting) and at no time have any DTC's been reported.

Today I had some time and found that adjusting the rear height sensors from lowest to highest made absolutely no change.

One question that I haven't seen mentioned is:

"If one of the rear height sensors fails, what is the default response from the air-suspension ECU? Does it simply default to max height on both sides?"

If it does, this would answer my question: "Why is this problem affecting both sides equally. Surely both sensors can't have failed simultaneously?"

I did a test btw to see if raising one side of the rear on a jack would affect the other side. The result was that it does, but only by a smallish proportion.

I'd like to test each rear height sensor. Does anyone know the resistances I should expect across the 3 pins?

As I said, HELP!!

Seriously, any advice would be gratefully received.

Reagrds,

Mike

post-25214-127659972762.jpg

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I have no experience in this, but somethin similar happened to my brother's Omega, as that had self levelling suspension, a fuse went and it just pumped it right up a good foot higher than normal

may be as simple as that, altho, different car means it could be somethin else causing it...?

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I have no experience in this, but somethin similar happened to my brother's Omega, as that had self levelling suspension, a fuse went and it just pumped it right up a good foot higher than normal

may be as simple as that, altho, different car means it could be somethin else causing it...?

Thanks Rory but I've checked the fuses - there are quite a few of them. There is also a relay and a fusible link for the air-susp. - not sure how to check the relay apart from substitution.

Any other ideas are welcomed.

Mike

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Ok, I've been thinking this through a bit and would appreciate your thoughts.

Going through the possibilities:

1. The compressor is ok as the back is pumped up to the max and I can still hear the compressor operating from time to time.

2. Actuators (is this the same as "ride height control valves"?)can't be at fault as a failure here would imply low suspension not high.

3. Height sensors could produce this problem as the failure of one would lead the suspension ECU to pump up the back to the max (if you think it through that must be true)

4. Exhaust valve failure would not allow the pumped up back to go down BUT if that were the only fault then how could it get pumped up so high in the first place. Also, as there is only one exhaust valve, why hasn't the same thing happened to the front?

5. The struts themselves can't be the problem as a leak would give low height not high.

6. I guess it could be the ECU but I'm sure that's unlikely.

Finally, the back does occasionally go down about halfway implying that it's an intermittant problem which is more likely to be a dirty/corroded sensor.

Does this make sense?

I'm favouring the sensor as the culprit in the absence of any ideas.

I guess I'll try to remove them one by one and test them as recommended in the manual.

I believe that I should be safe to drive with the sensors removed, would you agree?

Phew!

Regards,

Mike

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Just to update this situation, this morning I just dropped a customer off at Heathrow and as I was driving away the car really started bouncing up and down. I think what happened is that the compressor operated again even though the back is jacked right up bringing the air pressure up to maximum - ie. no more increase in height just pressure.

I drove around for a while thinking that this was not acceptable for my next passenger when suddenly there is this great high pitched musical fart (sorry, I couldn't think of a better description) and I'm wondering what on earth is going on. However the ride immediately returned to "normal" (still jacked up) so I realised that it must have been the exhaust valve overload device releasing the excess air. I didn't realise there was such a device in the system but thinking about there must be to avoid damage to all the pressurised components.

Anyway.....I got home ok (none of my customers have noticed anything amiss btw. which is good) and as I've a few hours before my next trip I removed both rear ride height sensors and tested them according to the manual. They both checked out fine. Incidentally, I've read a lot of threads talking about water ingress and various damage - mine were both completely clean inside as the lid seals with a rubber "O" ring. There was a very slight carbon build-up on the brushes which was easily removed but as I say the readings were normal - voltage rising nicely from 0 - 4.5 as the link was turned.

So....where does that leave me....there seems to be plently of wiring to test for continuity.

One thing I need to do whilst still on the sensors is to check for the presence of voltage at the relevant terminals on the Air-sus. ECU. I see that it's somewhere under the passenger side at the front. Has anyone found theirs? If so can you give me any tips for locating/accessing it?

Another question..... I haven't fully discounted the exhaust valve and I'd like to test it. The manual says to apply 12v to the terminals and see if it works. I took the wheel and wheel arch lining off yesterday to attempt this but could see no way of getting at the terminals, even to check the resistance let alone getting a pair of Battery wires in without sparks flying. Any suggestions??

Thanks for reading...please don't hesitate to give me your thoughts, I'm really not ready to hand the car over to a garage yet.

Mike

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Have you checked the front height sensor(s). I would've thought, if it sensed the front was (incorrectly) high, then it would raise the back to match? So maybe you are looking at the wrong end of the car?

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Have you checked the front height sensor(s). I would've thought, if it sensed the front was (incorrectly) high, then it would raise the back to match? So maybe you are looking at the wrong end of the car?

Tigerfish,

You could be right, I must do that, will let you kow how I get on.

In the meantime any help with locating the air-sup ECU would be invaluable as I just can't find it.

Regards,

Mike

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On a US vehicle, it is item number 89293 on the first diagram. The bracket in the 1st diagram is # 85999A in the 2nd diagram. It shouldn't be too far different for a UK one.

LS430ECU.png

LS430ECU2.png

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Thanks Guys,

But I still couldn't find it, Eventually I found this pic in the air-con section/blower unit removal. Hopefully I can find it now as it will be a boon to further diagnosis.

The other connector I'm having trouble finding is the "short block". The instructions say, "remove passenger scuff plate and pull back carpet". Well I've done that on all 4 scuff plates and I cant see any connector. Has anyone done this successfully?

Thanks again for all your help.

Regards,

Mike

post-25214-127684958295.jpg

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  • 2 weeks later...

Hey Mike. Did you resolve the problem? Have you ever tried to change the dampening force through the rod of the actuators? Yesterday i tried to soften the ride, but haven't noticed any difference since then. According to the service manual, the rod has to be turned to left, if you want to soften the dampening. I tried that with the actuator's rod. I'm not sure whether i should do that with the strut's rod also... Help :)

28rjgxz.jpg

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  • 2 weeks later...

Sorry Brio, I missed your post.

Yes, I have partial success with this issue in that I have a temporary solution which is not ideal but fine fttb.

I've left the air-sus and headlamp levelling fuses out to prevent the "failsafe" dragster/superhard supension situation and have adjusted the ride height and absorber damping manually.

To answer you question:

1. You can adjust the damping by turning the rod in the absorber unit. You will have noticed that you have to turn the actuator by a similar amount to enable you to refit the actuator.

2. Assuming you have left the air-ride system operational, any manual adjustment you have just made will be over-ridden straight away by the system.

3. The trade-off for operating it manually (ie. removing the fuse) is that you lose the anti-dive/squat/roll capabilities so when you brake the nose dives, when you corner the car rolls and when you land after going over a hump the whole car may bottom out.

Having said that:

1. I've been driving for weeks like this with minimal disruption - I'm a very gentle driver, and

2. There has been no reduction in my ride height showing that the air side of the system is sound.

There is an alternative to the method of manual adjustment of the damping we have just mentioned - this is paricularly helpful for the rear as it saves removing the seating etc.

This method involves applying Battery voltage to the actuators' terminals on the ECU plugs. This has to be done in sequence as there are several solenoids in the actuator and need to be enlivened in the correct order. Full details are given in the worshop manual which is amazingly helpful when you find the relevant page.

Hope this helps.

Kind regards,

Mike

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  • 5 years later...

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