The primary mission of the air suspension system is the following for the rear suspension under loaded and unloaded conditions:

The air suspension system consists of the following items:

The air suspension module controls the inlet valves, the air suspension relay and both compressor assemblies to keep the rear suspension of the vehicle at the correct design height under loaded and unloaded conditions. The air suspension module will determine if the vehicle needs to be raised or lowered depending on the detected height changes determined by the left and right rear suspension position sensors. The leveling function will be disabled when any door or lift gate is open or when the inflator is being used.

When the vehicle is raised, the inlet valves are opened and the compressor relay is activated to start the compressor assemblies in order to inflate the rear air springs. Before both compressors are activated, the exhaust valve is opened momentarily to release air from a central chamber located within the valve assembly. Once both compressors are activated, the chamber is charged to a designed air pressure before the inlet valves are opened, which prevents lowering of the rear suspension caused by air exhausting from the rear air springs into the central chamber. As the rear suspension approaches the design height, both compressors will remain activated but only one inlet valve is open at any given time depending upon which side of the vehicle is not at the correct design ride height. Each inlet valve is switched closed and the compressor assemblies are switched OFF as soon as the design ride height is achieved on both sides of the vehicle.

When the vehicle is lowered, the inlet valves and the exhaust valve are opened so that air is exhausted from the rear air springs. As the rear suspension approaches the design height, the inlet valves are pulsed ON and OFF while the exhaust valve remains open until the rear height of the vehicle meets the designed ride height.

The air suspension system consists of 2 compressor assemblies. Both compressors run simultaneously and are controlled by one relay. One compressor has the exhaust valve mounted on its cylinder head. Each compressor has its own thermal limit switch. The compressors are a positive displacement air pump, powered by a 12-volt DC permanent magnet motor. A thermal limit switch is included to protect each compressor from being damaged as a result of each compressor running so long that it becomes overheated, which may be caused by excessive use of the inflator or a faulty air suspension relay. The thermal limit switch is normally closed and provides a ground signal to the air suspension module. If there is an overtemperature condition the thermal limit switch will open and signals the air suspension module to deactivate the compressor relay. The compressors will stop running and a DTC will set. As long as both compressors have not been damaged, the thermal limit switch will close, clearing the DTC, as the overtemperature condition returns to normal leading to both compressors operating under normal conditions.

Intake air for the compressors is drawn through an intake filter and line that is attached to the fuel filler pipe in the left rear wheel area. The air compressor assemblies are mounted to a bracket that is located under the rear center of the vehicle. The compressor air dryer is mounted next to the air compressors. It contains a moisture absorbing chemical that dries the compressed air before it is delivered to the rear air springs. Moisture is removed from the dryer and returned to the atmosphere when air is exhausted from the air springs during vehicle lowering.

The air suspension control module (ASCM) will conduct several self tests at every ignition activation, while other tests do not commence until wheel speed is detected at the wheel speed sensors. Any malfunction detected by the ASCM causes a DTC to be set and the driver information center (DIC) to display the SERVICE SUSPENSION SYSTEM message. The ASCM communicates with other modules in the vehicle via GMLAN. To prevent energizing the electronically controlled air suspension relay or the LR and RR inlet control valves during normal ride motions the ASCM provides a calibrated delay before leveling the vehicle.

Both air compressors are controlled by the air suspension control module (ASCM) by the use of a relay. The relay and wiring are protected with a 60-amp fuse. The ASCM will only activate the compressor relay when the engine is running.

The rear air suspension sensors are potentiometers which detect height changes at the rear of the vehicle. The sensors relay the height changes to the air suspension control module. The sensors are mounted to the frame at the rear wheel area on the left and right sides. The activation arm is attached to the upper control arms of the rear suspension.

Extended ride height (ERH) is used to increase vehicle ground clearance. When the ERH switch is activated the vehicle will raise 2 inches at the rear. The extended ride height will only occur if vehicle speed is less than 64 km/h (40 mph) with the lift gate and all doors closed with the engine running. When the switch is activated the ERH switch indicator will flash while the vehicle is transitioning to extended ride height. When the vehicle reaches extended ride height the ERH switch indicator will be on continuously. The vehicle will return to normal design height when the switch is activated again and the ERH switch indicator will go OFF. The vehicle will automatically return to normal height if vehicle speed increases over 64 km/h (40 mph) and the ERH switch indicator will turn OFF.

The air suspension exhaust valve is used to exhaust air from the air springs and lower the vehicle. The air suspension exhaust valve is mounted on the head of one of the air compressors. The air suspension exhaust valve is controlled by the air suspension control module.

The inflator system consist of a inflator hose to provide a means of inflating objects, and an inflator switch with a switch indicator located in the rear compartment. The inflator will only function when the engine is running and the vehicle is in PARK. The inflator switch indicator will be illuminated with the inflator ON. The inflator function will have priority over leveling functions.

The air suspension system uses the air pressure sensor to monitor system pressure. The air suspension control module uses that signal to determine if there is a leak in the system and to maintain a minimum air pressure in the system.

The air suspension system has 2 inlet valves, one for the right air spring and one for the left air spring. The valves are mounted to the valve block with the air suspension pressure sensor and is located next to the compressor. The valves are activated and controlled independently by the air suspension module.

The LR and RR air springs are mounted in the frame in the same location were the coil spring is mounted for a vehicle without air suspension. Support pieces are affixed to the axle for the air springs.