GM Service Manual Online
For 1990-2009 cars only

With this feature, an electronically controlled air suspension system automatically keeps the vehicle level as it is loaded and unloaded. The system includes a compressor, two height sensors and two air springs supporting the rear axle.

The system also has an internal clock to prevent overheating if the inflator is used for prolonged periods. If the system overheats, all leveling function stops until the system cools down. During this time, the indicator light on the air inflator switch will be flashing.

The ignition has to be on for the system to inflate, in order to raise the vehicle to the standard ride height after loading. The system can lower the vehicle to the standard ride height after unloading with the ignition on and also for up to 30 minutes after the ignition has been turned off.

The compressor may be heard while it is operating when the vehicle is being loaded, and periodically as the system adjusts the vehicle to the standard ride height.

If the vehicle is parked for an extended period of time, some bleed down of the suspension is normal. Upon starting the vehicle, proper height will be achieved.

Overload Protection

The air suspension system is equipped with overload protection. Overload protection is designed to protect the air suspension system, and it is an indicator to the driver that the vehicle is overloaded. When the overload protection mode is on, it will not allow damage to the air compressor. However, do not overload the vehicle. See Loading the Vehicle.

If the suspension remains at a low height, the rear axle load has exceeded GAWR (Gross Axle Weight Rating). When the overload protection mode is activated, the compressor operates for about 30 seconds to one minute without raising the vehicle depending on the amount of overload. This will continue each time the ignition is turned on until the rear axle load is reduced below GAWR.