AHC woes (1 Viewer)

[AtinLango]

I routinely do 1,000 kms round trip. 800 km is smooth tarmac, 200 kms rough/bad unpaved.

Yesterday, i made the forward trip of 500 kms. I had no issues as always. I have nearly full tank of fuel since i refilled close to the destination.

However, after resting, i was helping someone transport 6 jericans (20 liters each) of water over less than a km, so i loaded them in the far end of the boot. Because rhe road was bad, i tried to raise the AHC from N to H. It tried raising, but failed back to N. Now it is stuck at N, with OFF blinking.

I disconnected the batteries and engine bay AHC fuse, and reconnected, but no help.

When i try to raise to H, it goes back to N, blinking OFF. I have not tried to lower to L because i fear it will get stuck in L, which is worse than the current condition.

My mechanic is 500 kms away, and i dont want to rush and bring him over. Yet i cannot drive this way because the ride is too rough.

What else can i try?

Is it possible that the AHC fuse in the cabin is blown? I do not know where it is located, otherwise i would have checked.

Your help is the only saviour. Many thanks.

 

[suprarx7nut]

The most common reason for failing to go into H is over-pressure. If you have not checked neutral pressures, they are very likely too high. The fix is free. You need to turn the torsion bar adjustment bolts clockwise. Try 5 turns first on each side. If it still has a problem, turn another 5 turns.

Side note: H is more harsh than N. If you are hitting the car on rocks, then you can use H. If the road is just rough, keep it in N. Lower pressures in the hydraulics and a lower ride height make for a smoother ride.

Use only as much lift as you need. Anything more is a waste.

 

[AtinLango]

Thanks. Will try this when i reach the next city, about 50 kms away.

The most common reason for failing to go into H is over-pressure. If you have not checked neutral pressures, they are very likely too high. The fix is free. You need to turn the torsion bar adjustment bolts clockwise. Try 5 turns first on each side. If it still has a problem, turn another 5 turns.

Side note: H is more harsh than N. If you are hitting the car on rocks, then you can use H. If the road is just rough, keep it in N. Lower pressures in the hydraulics and a lower ride height make for a smoother ride.

Use only as much lift as you need. Anything more is a waste.

 

[AtinLango]

I have spotted a fuse box near the accelerator pedal. Car is RHD.

Picture attached, but i cannot see AHC fuse. Where could the fuse be?

 

[AtinLango]

I left the batteries disconnected overnight. Starting the car this morning,, it still refused to go to H. Remained in N, but the OFF blinking stopped for a bout 2 km. Ride was perfect. But started blinking again, ride too bad.

 

[AtinLango]

Worst case scenario, can i drive in this state for 500 km without causing damage?

 

[uHu]

Worst case scenario, can i drive in this state for 500 km without causing damage?

Damage to others or damage to the AHC system? As long as you have enough damping to make the handling safe, you should be OK.

Have you checked the three height sensors? If all sensors and linkages are OK, you might just have too high pressures. You can lower the rear pressure by adjusting the sensor an inch down, as a temporary fix.

Time to read the great AHC thread, and get TechStream.

 

[scanderson76]

@AtinLango, did you not read what @suprarx7nut wrote? You most likely have a pressure issue. Did you remove the jerry cans and try to raise it to H? If not, give it a shot and if it raises up, you have your answer. Turn the torsion bars as previously mentioned until you can raise the vehicle with the Jerry cans in the back. Do you not have the proper tool to turn the torsion bars?

 

[Wilsil]

Get yourself a miniVCI and Techstream and check the pressures.
Normally what you describe is overweight for the AHC

 

[BullElk]

Just an innocent little FYI…. My AHC would also not go to H. Unlike you, I did lower it and it would not go to N. My solution was changing the two small O rings in the pump. It works perfectly now. You may want to try this when you get in a location to do so.

 

[AtinLango]

I left for the nearest town enroute back home about 500 kms away about 6 hours ago. I made a few stopovers.

A mechanic at the nearest town had promised over phone call that he would help with techstream and wrench for adjusting the torsion bars. When i reached him, he had none of those.

So i proceeded on my journey. It was a pain on rough road, but so smooth on tarmac. i actually enjoyed the ride on tarmac. Yet the car was (and is still) now stuck in L (rather than N) throughout. At first, this scared me stiff.

So as of now, thc car cannot move away fron L. I will hunt for techstream tomorrow.

 

[BullElk]

Definitive list of AHC maintenance items

I think you're confused. Keep the AHC, of course! :) In addition to AHC, use air bags. They are used together as a complimentary system. I am not suggesting you remove AHC. I rarely speak those words, haha. Hi Suprarx7nut I have just been chatting to a local company who are going to look...

forum.ih8mud.com

Look at post #895 by @IndroCruise in above thread. This is a fairly simple way of checking for AHC codes. Then you can go from there. The thread also has instructions on doing an “active test” to manually raise your vehicle.

 

[AtinLango]

I have spotted a fuse box near the accelerator pedal. Car is RHD.

Picture attached, but i cannot see AHC fuse. Where could the fuse be?

View attachment 3448544

Just trying to understand this fuse box (found in car interior near accelerator pedal). Where are the AHC-related fuses?

 

[AtinLango]

I finally got a mechanic with Techstream, but unfortunately he could not help much (if at all). Instead he said the problem is with ABS system. He said ABS and AHC are related. I am very much aware that I cannot allow anyone to tamper with a system which they do not know. I simply wanted to read the fault code(s), which we never even achieved.

When I went under the car with him, he listed for me the "visible" problems with the AHC system - that rear shocks are leaking (whereas there are no signs, and I replaced them a few months ago); that rear sensors have failed; and finally when we came back from under the car, he said the pump is malfunctioning.

Well, I had no option but to request him to try to adjust the torsion bars for me. We did 5 turns on each clockwise. The effect now is that the car is unstable and bumpy (moving up and down) on the rear, which was not the case before.

AHC is still stuck on L, and the OFF light blinking as it was before.

I decided to first take the car back home and make a reflection.

 

[AtinLango]

Note that my car had never had any AHC issue since i purchased it 5 years ago. I never even had the remotest fear of AHC issues since it was extremely stable and worked perfectly all the time. The only challenge was that the damping was getting a little bad - but was still within acceptable limits.

But things changed after i replaced shocks and globes a few months ago. The ride became so smooth and fun driving. Yet, I have also painfully now got 3 incidents of AHC getting stuck in L.

The first two incidents were easily resolved by cleaning off sludge inside the AHC pump and replacing the motor brushes respectively.

I am waiting to resolve this last incident.

 

[BullElk]

I think you should read the AHC codes by using jumper wire (paper clip) in the little black box in engine bay on side fender. Look at post #9 by @uHu in the thread below…

How to reset AHC pump or bleed air from the system?

Many thanks to this forum (Hoser,Hkeller,Lexusben Texasoiland Uhu in particular), I was able after grinding a 36 mm spanner down to 8-9mm thickness to change both the rear flat accumulators of our 2000 LC100 (not too difficult;just one sphere was a bear to get loose!). Now I am facing a...

forum.ih8mud.com

Since you are familiar with taking pump apart I suggest again to look at replacing the two small O-rings. That is cheap and easy. The silicone pliable o- rings are responsible for fitting snug and holding pressure. If they’re old and not sealing well, the pump will not hold pressure.

But first, easily, check codes as per the thread above.

 

[AtinLango]

I think you should read the AHC codes by using jumper wire (paper clip) in the little black box in engine bay on side fender. Look at post #9 by @uHu in the thread below…

How to reset AHC pump or bleed air from the system?

Many thanks to this forum (Hoser,Hkeller,Lexusben Texasoiland Uhu in particular), I was able after grinding a 36 mm spanner down to 8-9mm thickness to change both the rear flat accumulators of our 2000 LC100 (not too difficult;just one sphere was a bear to get loose!). Now I am facing a...

forum.ih8mud.com

Since you are familiar with taking pump apart I suggest again to look at replacing the two small O-rings. That is cheap and easy. The silicone pliable o- rings are responsible for fitting snug and holding pressure. If they’re old and not sealing well, the pump will not hold pressure.

But first, easily, check codes as per the thread above.

Thanks for that elaborate reply.

I am no mechanic by any measure. I only try to observe what mechanics are doing and try to copy for later use where possible.

I sm sure i can do active test if i see someone do the part of shorting the pins in the engine bay. That is my only difficulty.

My mechanic is expert in AHC pump. He can disassemble and reassemble even when blindfolded. But he also has serious shortcomings. He does not do well when a lot of science is involved. So things to do with AHC neutral pressures, graduation test, and the like are not on his menu. I try to teach him the science that i learn from this and other forums. Hs doesn't like them. This is my big dilemma. And interestingly, i have not yet spotted any mechanic here who knows AHC science, or even how to use diagnostics scanner really well.

My mechanic is coming tomorrow. I can nearly predict that he will want to open up the pump. Even if he gets a solution tomorrow, i am not sure of the sustainability. I have already developed fear of an otherwise wonderful AHC system.

 

[suprarx7nut]

I wonder if you have more sludge on the pump.

AHC is much, much easier with Techstream. If you don't have techstream and a cable with you (or an app and an ELM dongle) then you're pretty SOL if things go wrong.

If you're traveling anywhere off the beaten path with AHC, you should have your laptop and techstream with you. If you don't, it's a liability.

 

[AtinLango]

I wonder if you have more sludge on the pump.

AHC is much, much easier with Techstream. If you don't have techstream and a cable with you (or an app and an ELM dongle) then you're pretty SOL if things go wrong.

If you're traveling anywhere off the beaten path with AHC, you should have your laptop and techstream with you. If you don't, it's a liability.

This sounds like the absolute truth. My recent AHC woes could simply be because i haven't used techstream to troubleshoot, and no mechanic here seems to know how to effectively use techstream.

Being a computer programmer / software engineer myself, there is no doubt i will easily use techstream if i land on one. That should be my ultimate target.

It should not surprise anyone if they hear a lot of bad experience of AHC. Honestly, it is just because many people dont understand AHC, otherwise it is the best system in my view. Few can understand or troubleshoot AHC.

 

[J1000]

If the height sensor in the rear is broken that's your problem. Replace or repair it and then go from there.