Three common issues that are known to be the cause in most GX470 Automatic Height Control (AHC) failures are: air leaking from the system, a clogged or weak compressor pump, and the height control sensors. Any one of these faults can leave your Lexus lowered all the way to the bump stops, raised to the maximum height, or even leaning to one side.
The most common symptoms of air leaking from your suspension is either a lowered rear-end or your Lexus not raising when towing or hauling. The most common location for an air leak is the rear air springs, which you can check using a solution of soapy water sprayed on the folds of the rubber bellows. Make sure to check your air springs on multiple different height settings, the ridges of the bellows can hide pinhole leaks when collapsed. Spraying down your air lines all the way to the compressor will help you identify any other minor leaks in the tubing, and also helps to check if the line running from the compressor is properly seated.
Air Compressor Pump
Years 2003 and 2004 GX470’s have a specific Technical Service Bulletin (TSB) for the air compressor pump. TSB SU002-05 specifically corrects an issue with moisture seeping into the exhaust solenoid, contaminating your entire AHC system, and even locking it up in temperatures below freezing. Check the date code printed on the bottom of the compressor mounting bracket and make sure your compressor pump has been replaced. With a prolonged leak in your AHC, the compressor overworks itself and quickly wears out; if you hear it running more often or running longer than normal when adjusting your ride height, this would be the issue.
Height Control Sensors
The ride height control sensors on the Lexus GX470s are prone to failure in multiple points, so check yours regularly. The sensors internals can wear down and stop working, the attachment arm pivot can seize and break off from the frame bracket or the attachment point, leaving you with a very confused Lexus. When both height control sensors are faulty, the suspension control will completely shut off and will not work until at least one sensor is reporting the ride height again.
Fuses and Relay
Three fuses and one relay protects the AHC electronics. These components need to be checked and replaced when necessary. There is a 50 Amp compressor fuse, and 10 Amp air suspension fuse located in the main under hood fuse panel, with the AHC relay located in a sealed box attached to the side of the panel, and a single 20 Amp TEMS fuse under the dash.
How Suncore Can Help
Suncore Industries includes the GX470 air springs in our line of air suspension components and we also offer multiple variations of suspension conversion kits specifically for the Lexus models. Our trained technicians are happy to help you with your suspension issues, from diagnosing to converting, and everything in between. Give us a call today!