98lx470 AHC question

[beachbumin]

Found a local 98 lx470 and pounced on it last week. In the process of getting everything together for a major baseline and have a question on the AHC.

When I test drove it the buyer said he never used it and it had some issues. I pressed the button to rise to high and it did with no issues. After that I got out and looked around and all seemed fine. A few minutes later while looking over the rest of the truck the front drivers side dropped to N then the rest slowly followed. There was the blinking off light but to my knowledge the truck never dropped all the way to low.

Has anyone seen this type of issue and would a AHC flush be any good here? I got into this fully expecting the rip out of the system but if it is able to still work it would be preferable. Thanks for the help!

 

[jdayment]

N is normal height it shoouldnt just drop to low. Is the fluid level correct and i dont think my off light blinks unless i turn it off. Have you done a search?

 

[LXG8R]

Getting your hands on the Techstream software and a usb to OBDII would really help with a diagnosis of the AHC health.I have not had that issue on mine but Techstream did inform me that the AHC pump was taking too long to raise the vehicle.

 

[PADDO]

Found a local 98 lx470 and pounced on it last week. In the process of getting everything together for a major baseline and have a question on the AHC.

When I test drove it the buyer said he never used it and it had some issues. I pressed the button to rise to high and it did with no issues. After that I got out and looked around and all seemed fine. A few minutes later while looking over the rest of the truck the front drivers side dropped to N then the rest slowly followed. There was the blinking off light but to my knowledge the truck never dropped all the way to low.

Has anyone seen this type of issue and would a AHC flush be any good here? I got into this fully expecting the rip out of the system but if it is able to still work it would be preferable. Thanks for the help!

If the vehicle was in H, engine running with doors shut and it commanded itself to lower then I'd be looking primarily at a failing height sensor, excessively high neutral pressures and possibly entrained gas within the hydraulics. Couldn't discount internal leakage either. Replacing old, contaminated and degraded AHC fluid is always a good thing, particularly if it's got a gut full of gas in it and is allowing some compressibility - it may solve your problem - but it sounds like your vehicle would benefit from an overall AHC makeover including a proper fluid exchange and bleeding, neutral pressure corrections and confirming the height sensors are still fully serviceable by reviewing their feedback in Techstream.
I suspect the PO had very limited to no idea on the AHC and AVS because the statement "didn't use it" is very misleading. Unless the system is disabled or otherwise non functional it will automatically correct front or rear heights to the pre determined positions due to load variations (that's the Active part of AHC), stiffen the front shock actuators during braking, stiffen shocks during cornering etc and the damping is constantly being varied whilst in motion (the Adaptive part of AVS) using the same hydraulics and ECU. Just because an owner doesn't raise or lower regularly the system is still "being used".

 

[beachbumin]

The seller seemed to not know anything about the system. He did mention that he saw no difference between comfort and sport setting. I have looked all over for a basic how to on the AHC but have came up short so far.

As of now, I am no messing with it until I am prepared to either fix or remove the system.

Thanks for the tips. Can't wait to get further into this.