AHC Suspension strange behavior (1 Viewer)

[Kav]

Hello,
I have a 2003 LX470. I currently am letting my father drive it as he needs something better in the snow. He is telling me that the AHC was not working. I came out to see what he was talking about. The truck was very low, he said it was higher than he’s ever seen in the morning before. I took it for a short drive and when I went over a small bump the truck seemed like it bottomed out in the rear. I am probably leaning towards replacing the AHC with something else like an OME setup. I am wondering if this is something that can be repaired easily though. has 305k miles.

 

[Rhetoric]

Pleaaaaaaaaaaaaaase search for threads here on how to troubleshoot the AHC. Unless the system is completely rotten from rust they can be brought back into working condition with the amazing knowledge folks have here… for a lot cheaper than putting a garbage suspension on.

-Get Techstream and a cable
-Start reading posts by PADDO

 

[suprarx7nut]

Hello,
I have a 2003 LX470. I currently am letting my father drive it as he needs something better in the snow. He is telling me that the AHC was not working. I came out to see what he was talking about. The truck was very low, he said it was higher than he’s ever seen in the morning before. I took it for a short drive and when I went over a small bump the truck seemed like it bottomed out in the rear. I am probably leaning towards replacing the AHC with something else like an OME setup. I am wondering if this is something that can be repaired easily though. has 305k miles.

OME is hot garbage for the 100 unless you've got 1000 lbs of armor on the car.

Sounds like you have a bad height sensor. Easy fix. Might also be dead globes. Another easy fix. Could tackle both for under a grand.

AHC is much nicer than anything else you're going to install. Spend a few minutes to learn about it. You'll want Techstream or an advanced OBD2 reader to pull codes and data, but from there the system is relatively easy to work with.

 

[BullElk]

Pleaaaaaaaaaaaaaase search for threads here on how to troubleshoot the AHC. Unless the system is completely rotten from rust they can be brought back into working condition with the amazing knowledge folks have here… for a lot cheaper than putting a garbage suspension on.

-Get Techstream and a cable
-Start reading posts by PADDO

OME is hot garbage for the 100 unless you've got 1000 lbs of armor on the car.

Sounds like you have a bad height sensor. Easy fix. Might also be dead globes. Another easy fix. Could tackle both for under a grand.

AHC is much nicer than anything else you're going to install. Spend a few minutes to learn about it. You'll want Techstream or an advanced OBD2 reader to pull codes and data, but from there the system is relatively easy to work with.

^^^^^^^^^ Adhere, adhere… I tell you adhere!!

 

[smoltz]

The ABCs of AHC - How to Measure, Flush, and Adjust all in one place

I initially put this in the Definitive list of AHC maintenance items thread, but at almost 800 posts long and growing, it's going to get buried and the thread itself is very unwieldy. In an attempt to make as focused a summary as possible, I present "The ABCs of AHC." It's intended as a...

forum.ih8mud.com

You'll need techstream or a scan tool capable of reading AHC system.

 

[Wilsil]

^^^ what they said

 

[Kav]

Thanks everyone. I will do some researching.

 

[Kav]

OK, I have decided against replacing the AHC, as many people have suggested. I think based on what I have read it may need to have the rear height sensor replaced. It probably should have a AHC fluid flush too. Should I replace my height sensor first? The reason I ask is because currently I cannot raise or lower the vehicle in order to flush the fluid as detailed here. I know I need to check things with Techstream but I am not close to the vehicle any more So I am trying to find someone to fix it for my dad.

 

[uHu]

I would make sure I have working height sensors first of all.
To help you with finding the fault(s), I'll list the most common ones.
What happens on all AHC vehicles is that :
1 - The AHC pressure becomes to high because of lack of (annual check and) adjustment of steel springs, i.e. adjustment of front torsion bars and change of rear coil springs. (Check at least every 3 years)
2 - Height sensors wear out, i.e. that the carbon trace inside the lid wears through because of normal use. (10+ years)
3 - Globes loose their pressure over time. This does not affect the height adjustment in any way though, only the ride quality and suspension travel (Which also means loss of damping and dangerous handling). (10+ years, depending on point 1)
4 - Height sensors links/arms can be damaged because of external mechanical influence, like a branch or stick bending a link arm.
Then some faults that are more frequent under influence of water and salted roads:
5 - Height sensors corrode inside, giving same symptom as a worn out sensor.
6 - Cables to sensors and valve body fail. Most commonly the small cables from sensor to fender, or the 2-3 plugs (at the left rear) between ECU and valve body.
7 - Height sensors links/arms corrode and break or ball joints get stuck and break.
8 - Leaking pressure pipes because of corrosion.

 

[Skruf]

It will only be toyota/lexus dealers who will attempt to fix it and all they'll do is throw new components at it.

Sensors are wear items, your rig is 20 years old, reasonable to bite the bullet and replace all of them and see if that fixes it.

 

[uHu]

It will only be toyota/lexus dealers who will attempt to fix it and all they'll do is throw new components at it...

Can you elaborate? (No other people/garages/mechanics/dealers?)

But yes, I agree that dealers' garages will just start changing parts, starting with the most expensive. When everything is changed, or the customer is broke (whichever comes first), they give up. And then the fault is corrosion in plug, e.g. I guess that's when we see the difference between an amateur and a professional; the former fixes it because he loves what he's doing, while the professional just tries to make a salary and wouldn't even be bothered to read the FSM.

 

[TexLXCRZR]

If you decide to remove I went with Eibach and OEM TB's for the closest ride quality. Very happy with the setup and happy to be rid of the aging complications of the system. It certainly has its merits but for me I can do without that level of complication in my suspension in favor of a more robust system.

 

[nineosixdave]

I would make sure I have working height sensors first of all.
To help you with finding the fault(s), I'll list the most common ones.
What happens on all AHC vehicles is that :
1 - The AHC pressure becomes to high because of lack of (annual check and) adjustment of steel springs, i.e. adjustment of front torsion bars and change of rear coil springs. (Check at least every 3 years)
2 - Height sensors wear out, i.e. that the carbon trace inside the lid wears through because of normal use. (10+ years)
3 - Globes loose their pressure over time. This does not affect the height adjustment in any way though, only the ride quality and suspension travel (Which also means loss of damping and dangerous handling). (10+ years, depending on point 1)
4 - Height sensors links/arms can be damaged because of external mechanical influence, like a branch or stick bending a link arm.
Then some faults that are more frequent under influence of water and salted roads:
5 - Height sensors corrode inside, giving same symptom as a worn out sensor.
6 - Cables to sensors and valve body fail. Most commonly the small cables from sensor to fender, or the 2-3 plugs (at the left rear) between ECU and valve body.
7 - Height sensors links/arms corrode and break or ball joints get stuck and break.
8 - Leaking pressure pipes because of corrosion.

All,

I am experiencing an AHC problem, also. 2003 LX 470. Having read posts years ago, I remember the stories that say, when AHC goes, replace with (name your 4X4 suspension vendor here). The above information is really encouraging because up until the last 4 months, I loved the way my truck drove.

I did a bleeding of the suspension a few months back but it seemed there was still air in the system. So I took the truck down to the Toyota dealer and asked them to bleed the system.

After review the dealer said, "Need new rear shocks. They are leaking. $1,900." I thought about it, and if I could get the drive back for $2K what the hell, I am going to put another 250K miles on it. "Go ahead," Is said.

Hang in there the story is just getting going.

Two days later I get a call. "Ah... we drove the truck and the rear did not fix. Our fault. You need front shocks, too. Another $1,900 but it was our mistake. How about another $1,000?" I thought about it and said,"My truck back like new for $3K. Sure, go ahead and do it."


Next day, another call. "The shop foreman who has been here for 30 years is looking at your truck. He said, this repair will be $9K."

Ah... not going to spend that.

The dealership was amazing. They said, our fault. Pick your truck up, new rear AHC shocks, you don't owe us a dime for any of the work we have done. You will need to replace with standard shocks at another shop.

So then I read this thread. I have done the fluid changes on this AHC. Always with original Toyota fluid. I have never seen a leaking shock or globe in the past. So now I am thinking, I got new rears, there is some good advice above on what might really be wrong. Where should I go from here.

Other changes. I bought a replace "ride switch" in the center panel and replaced it. No change. The truck height control switch still works and the truck raises and lowers. The fluid is clear and full.

Could this be a globes problem or height sensors problem I should try and fix?

One last item, Toyota said that my pressure reading should be 7 and mine reads 4.

Sorry for the thread hijack. Any advice would be appreciated.

 

[Wilsil]

First of, $1900 for 2 shocks? I was quoted AUD$165 for one AHC shock from the Lexus dealer 2 years ago.
Get a Techstream unit and get the measurements yourself.

How-To: TechStream In 5 Minutes

Getting Techstream up and running can be a bit of a pain. Hopefully this helps someone get started quickly. Step 1: Purchase an OBD-II / Mini-VCI interface. - I have sold out of my cables and supply chains are back in order, so no reason to purchase more. Anything like this will work: Mini-VCI...

forum.ih8mud.com

Here is the link if you haven't read it yet.
Changing the front pressures is easy by adjusting the torsion bars.
The rear is a bit harder but you can add a spacer or swap the coils with non-AHC Landcruiser ons as I did 8 years ago,