Intermittant AHC issues

[imprator]

The rear sensor is mounted above the rear axle, just off-centre as I recall. It is a small plastic box with a metal lever arm coming out of it, and an electrical connection plugged into it. The box is attached to the axle, the end of the lever arm to the chassis (or vice versa, I don't really remember which).

The front sensors are located inside each front wheel well, behind the road wheel and above the axle line. The box (same description as above, but slightly different configuration) is attached to the suspwnsion assembly, the lever arm to the chassis (but again, perhaps vice versa).

I don't know for sure whether you can make things worse, but I think you probably can if you don't refit the sensors exactly as before (each sensor's lever arm has an adjuster on it). Also, if any sensor is sufficiently corroded inside you can probably render it completely inoperative by dismantling it. My corroded sensor was so far gone that the little springs etc. pretty much disintegrated as I removed the lid (thereby relieving the pressure that was keeping them partially in one piece). Others with more experience may be able to offer better advice.

 

[Jim_Chow]

I don't recall mine having a box. I took a look underneath recently with intention of sealing the sensors but seem to remember them being encased in something like a rubber boot, couldn't really see how moisture could get in easily.

 

[hkeller]

Damn, the suspension is at it again. It's been a year or so since I replace the rear accumulators and six months before that I replaced the front. What the hell is going on?! The ride is bouncey again.

Will bleeding the system help? I have two cans of fluid in the garage. Or, is changing the accumulators the only way to fix this.

ARRHG! Toyota helped with the first issue, but I doubt they help again. I'd like to keep this rig, but I can't spend 4 grand every 18 months to fix these damn things.

Flame on, but my Jeep cost less to keep on the road and it had 160,000 miles on it.

 

[hec4x4dk]

Try sensors...

I very much doubt the accumulators/spheres are cause for consern. Lack of suspension movement is to my expirience the sensors that does not recognize the vehicle being raised, and thus the AHC system keeps pushing hydraulics into the system (and the accumulators), leaving no movement (suspension) at all.

Vehicle would be very high in at least one end. Lowering AHC and turning off vehicle may help shortly - accumulator faults would not be periodic, sensor faults tend to be.

Sensors are expensive anyway, but far from 4G. My expenses on the sensors could be thought of as comparative to replacing dampers a couple of times - not all that bad after all.

Good luck...

 

[hedydd]

It should stay in low up to 9 mph. Does your manual actually "say" it will go to N immediately once you start moving? Might want to re-read.

There should also be a switch to prevent it accidentally raising for use in restricted headroom areas such as multi-story car parks or garages.

 

[hkeller]

Regarding it possibly being a problem with the sensors: last time I had this issue, replacement of the accumulators cured it. This indicates to me that it was in fact the accumulators and not the sensors. Thoughts?

 

[uHu]

Yes, some thoughts:
When, last time, you had 12 grads difference/change on the spheres test, the spheres are not busted, according to the FSM. And according to my limited experience. That is IF the steel springs and height settings are OK. Maybe the garage made more money on changing the spheres instead of only the sensors....

Some Q's:
How is the levelling working?
Is the rear or the front abnormally high or low?
How many graduations do you get on the spheres-test this time?

The spheres would get a greater share of the load as the torsion bars and coil springs weaken over time. Have you checked the neutral pressure of the AHC fluid front and rear?
(I checked mine 3 weeks ago and found the pressure a bit high. Turning the TBs 1.5 turns each fixed the front. The rear is a bit more work to rectify, normally means changing the coils.)
When the pressure increases, it means that the gas spheres would be compressed harder, and take more abuse.

Anyhow, bleeding is quick and easy.
Checking neutral pressure is also easy with e.g. a LSPV test kit. Just takes a bit of time with attaching and detaching the meter, while bleeding each time. Much easier with a Toyota Tester.

PS
Using the terms from the FSM, where the "spheres" are the gas springs (1 for each wheel), and the "accumulator" is the cylindrical thingy on the left frame rail. https://forum.ih8mud.com/showthread.php?t=60619

 

[uHu]

Thanks for all the comments and advice. One more question, where exactly are the sensors located and can I make things worse by taking them off and inspecting them, then remounting them? By the way, after all the problems, the system has worked flawlessly for the past week, but I am guessing that I will see the problem again. Thanks

How did this end?
Did you have it fixed?
Is there anything to learn from your experience?
What's the current status?

 

[hkeller]

uHu:

Thanks for the thoughtful reply.

The leveling works fine when you push the button to move to high or low. However, the car has been somewhat erratically self leveling when stopped at a light, etc.

The car is not abnormally high or low and looks level when parked.

I have not checked graduations yet. I will try to do that tonight.

It seems I have plent of up travel in the front, but very little down travel. The rears seem better, but not as good as normal.

My front right shock is leaking just a tad (I can tell by a slight film of oil on it). I wonder if this is effecting the system.

 

[loum3]

uHu--thanks for asking. Things seemed to clear up on their own for a few months, but I have begun having problems again. The suspension seems to raise and drop okay although it seems to take a long time and sometimes "catches" on the way down. Also, it rides very stiff from time to time (makes me sick when on the highway). Moving the TEMS switch has no effect. Then a really strange thing happened this weekend...while driving very slowly in a parking lot and turning into a parking space the right front side dropped quickly all the way down. After sitting for a couple hours, I was able to raise it back up and other than the suspension being tight and unadjustable. Any chance this could be electrical?

 

[hkeller]

Well, I have six graduations of change between low and high. Thoughts?

 

[r3run33]

wow loum sorry to hear of the troubles i have an 06 lx and sometimes it behaves on its own also but noway as much as yours but i noticed and check this mine seems to go off with the weather cold and damp not supper cold but 20 to 30 f. You guys should be having these temps now yes? Now mine never adjust that i know off when moving; at stop lights sometimes. Now mine does work a recent trip to home depot i loaded up with doors in the back and it was way loaded down once i started the truck it leveled out fine and then vice a versa after emptied out. Ican hear the motors working also sometimes also.

 

[r3run33]

i forgot to ask this do you have an extedned warranty?? If not you may just want to switch to a regular system; slee has done them before and has stated its very easy.

 

[uHu]

uHu--thanks for asking. Things seemed to clear up on their own for a few months, but I have begun having problems again. The suspension seems to raise and drop okay although it seems to take a long time and sometimes "catches" on the way down. Also, it rides very stiff from time to time (makes me sick when on the highway). Moving the TEMS switch has no effect. Then a really strange thing happened this weekend...while driving very slowly in a parking lot and turning into a parking space the right front side dropped quickly all the way down. After sitting for a couple hours, I was able to raise it back up and other than the suspension being tight and unadjustable. Any chance this could be electrical?

Pretty sure this is a height sensor issue, which makes it kind of electrical.
Open them and have a look. Piece of kake.

 

[uHu]

Well, I have six graduations of change between low and high. Thoughts?

Ya, I think you have to check the neutral pressure.
Because the steel springs are worn after several years and miles, the pressure in the AHC system will be higher, making the gas more compressed. This results in less comfort, "stiffer" ride, shorter suspension travel (the gas spheres bottom out).
For the front you can adjust the TBs to the right pressure. For the rear you ought to change the springs if the pressure is more than 20 % to high unloaded, or, if you want to be able to take on the maximum load, change them if the pressure is over the specified area at all.

If your spheres fail after 12-18 months, there must be something else than pure AHC liquid in your veins. (Which reminds me: use surgeons gloves when bleeding the system. The AHC fluid will dry out your skin so that it cracks up like a dried up pancake. Not nice!)

 

[r3run33]

yiickkss my 06 was just in for sevice and i mentioned the ahc; they checked it out and the height sensors were bad. Mine is covered under warranty (31kmiles) but this might be an issue with the 06's anyone else have this problem with an 06 lx or lc i thingk both lx and lc had them standard for 06 and 07

 

[lextechautomotive]

There is a TSB issued by Toyota/Lexus that addresses this concern. it consists of new sensors and improved wires harness to sensor

 

[hkeller]

LexTech:

Which concern does the TSB address? I am going to try to get to the dealer next week to have them check mine. Do you have the TSB number? Thanks!

 

[r3run33]

hello guys sorry been busy with hoiday stuff. I looked over my service stuff no parts #'s listed but lots of items on there and all say warranty under the heading of the ahc. I did not asked what was replaced or fixed; the service part was already closed and i just gave them back the loaner. Sorry i know this is bad on my part

 

[Texasoil]

AHC Issues

Erratic height adjustment is almost always height sensor problems Seems water gets into some of them. LC-100 uses a different part and seems more of a problem. 2006 LX-470 has a TSB out about it.

The AHC fluid is a highly refined hydraulic oil. In a pinch, use 5W engine oil or the lowest viscosity hydraulic oil you can find. NEVER use brake fluid, antifreeze-coolant or ATF.

Low accumulators will always ride badly over bumps. Sagged rear springs make things lots worse.