AHC going?

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Aug 30, 2006
Santa fe, New Mexico
Greetings wise people.

So I took my rust 99 LX rust queen out desert tracking near Truth or Consequences NM. 680 miles between highway and off road and I LOVE it. Amazing! And it fit my whole family!

But while there I noticed I couldn’t get it into Hi on the ACH unless I was moving slowly. Park was a no go. I get back and decide to do the ACH test and I can’t get it to go solid light low quickly at all. I had to move it forward very slowly then back very slowly then pro and after about five minutes it went.

Now to get it to go into high I had to do basically the same thing. It took for ever, nothing seemed to happen in park, once I began moving back and forth slowly it eventually went.

Now the fluid is way above max in low and right at max in high. This was not the case a few weeks ago when I checked. I don’t know if someone added it at a shop or what.

When going into high I heard a few thunks while in drive with my foot on the brake.

Any ideas wise cruiser people?

Attached are how high the fluid is in low and in high.


You'll need to have all of your doors closed (including hatch, I believe) for the AHC to adjust via the button. So if you were looking out an open driver's door to see if the clearance was changing, it wouldn't work.

AHC will not travel above ~20ish MPH in low or high mode without modification.

Have you had the truck serviced by a Toyota tech recently? I think it's unlike anyone would have added fluid to the reservoir; it's not a common, on-hand fluid.
This was not the case a few weeks ago when I checked. I don’t know if someone added it at a shop or what
If someone added some fluid other than Toyota/Lexus AHC fluid then your system is most likely sunk. I’m not sure how to tell after the fact. You could try changing out the fluid in the system now but I don’t have much faith that the pump and such would bo okay long term. I’m sure the computer will have a code for the poor pump performance but not sure if you’ll get any more information from it. Good luck. Worse case you get a nice lift kit.
Putting the truck into LO will cause fluid to be displaced into the under-hood reservoir - hence the increase you're seeing the fluid level in that mode. I'm skeptical that the back and forth is having any true effect, most likely just a red herring. Are you able to hook up to TechStream or an OBD-II reader to pull any codes? Without codes or data from the AHC ECU, we can take all kinds of guesses but that doesn't sound like a problem you'll be able to get a solid answer on just by description alone.
Ok thank you. I did not know that about the open door! Huh! Probably a safety precaution.

Yes, a Toyota place that changed the spark plugs and told me it was too rusted:). I wonder if they topped it off.

I do not have anything to pull codes. Darn it. Is it expensive?
That kit does not include new torsion bars, which you'd need if you were going to convert. Your lift is going to be dependent on your spring in the rear and how you set your (new) torsion bars up front. You won't have L/N/H anymore, it'd be a set height and stay there.

Check the FAQ thread at the top of the forum page, there's a ton of info about conversions here.

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