Truck "squats" at lights - AHC I'm assuming?

[Jeff Elliott]

Hi All -

New to me 2011 LX570 that I've been working preventative maintenance on recently. It has developed a tendency to "squat" when coming to a complete stop at a stop light. The rear drops somewhat abruptly.

I'm assuming this is AHC related? I did a code scan and got a code of "rear AHC sensor..." something... I believe it was not present currently but had occurred previously.

Anyone ever encountered this before and, if so, any suggestions on how to attack it?

Thanks!

 

[TXMeatball]

Normal, AHC likes to adjust itself at stoplights. Can either drop or raise depending on the mood.
Make note of the code, clear it, and see of it comes back.

 

[lx200inAR]

I find it happens a lot when you come to a stop on a slope as well. But it is normal behavior. Usually happens after being stopped and foot on the brake for 3-5 seconds. It would be interesting to have a data reader to see how often the AHC computer calls for height changes while normal driving.

 

[Jeff Elliott]

Thanks folks!

 

[radman]

Do you have a lot of gear in the cargo area? I've noticed that my front usually adjusts unless I'm loaded up in the back - then, the rear drops.

 

[TeCKis300]

Agreed normal. Especially stopping from higher speeds on a downhill, perhaps like an exit ramp off the freeway. Reason being weight transfers to the front under braking, causing the rear to naturally lift. Add in the downslope. Then combine with brakes and stiction applied against the suspension holding the rear up just a bit more when the vehicle comes to rest.

AHC height sensors will register the added height at the rear and attempt to correct, which is what you're feeling.

Can be avoided somewhat by not holding the brakes as tight when it comes to rest, or letting it roll out a bit more, relieving any stiction in the suspension. Some of it may also be due to AHC coming up to normal height from the hunkered down freeway heights, combined with dynamic situations which puts it up too far, which it then adjusts for.