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:

Important: The Air Suspension System must have a voltage supply of at least 12.6V to operate properly.

The Air Suspension System will maintain the rear D height within 4 mm (0.15 in) in all loading conditions and the leveling function will deactivate if the vehicle is overloaded. The side to side D height variation is maintained within 8 mm (0.31 in). After ignition is turned off, the air suspension control module (ASCM) will remain active for between 30 minutes and 2 1/2 hours. The system will exhaust pressure within 30 minutes after the ignition is turned off to lower the vehicle after unloading. In a temperature-controlled environment, the leakage of the complete load leveling system will not result in more than 1.4 mm (0.05 in) drop of rear suspension height at GVWR during a 24 hour period. If the outdoor temperature drops from +20°C (+68°F) to -5°C (+23°F), the rear D height may drop as much as 25 mm (1 in). However, the Air Suspension System should return to the specified D height when the ignition is again cycled to ON.

The air suspension compressor assembly houses the DC motor/air compressor, the air suspension control module (ASCM), an exhaust valve solenoid, and two air spring isolation valve solenoids. The ASCM sends a voltage signal to each height sensor and measures the inductance of the return signal to determine if one or both air springs need to be inflated or deflated. Before the compressor starts, the exhaust valve will be activated to provide compressor head relief. After this, the compressor relay will activate to start the compressor. When the trim height is achieved the relay will be deactivated. To prevent the compressor from overheating, the compressor operates on a duty cycle. If the compressor is requested to operate continually, the compressor duty cycle is limited to 300 seconds at maximum output for the first cycle. After this time, the compressor is automatically switched off for at least 92 seconds. Once this time has been met, the compressor will activate for 16 seconds and deactivate for 92 seconds. This 16 second/92 second duty cycle will continue until the compressor can remain off for more than 92 seconds. During this time, the indicator LED on the air inflator switch will be quickly flashing at a constant rate.

The air suspension compressor assembly has three different operating modes. Single Value Mode inflates and deflates the two air springs independently. This is the normal operating mode of the system. The system will enter Mean Value Mode when the sensor output indicates the difference between the D-height on each side is greater than 15.5 mm. In Mean Value Mode, the ASCM will average the signals from each height sensor to maintain an average trim height. If the measurement differential between the two D-heights reaches approximately 54 mm, the system will enter Lock Mode and no leveling will take place. This is to compensate for uneven loading of the vehicle or the vehicle being parked on an uneven surface. The air suspension compressor assembly also has a wheel change (jack) control that prevents the air springs from deflating completely. If the ASCM detects that one or both of the rear wheels has a D-height measurement of more than 235 mm, the system will enter Lock Mode and will suspend all leveling functions until the suspension is moved toward the frame.

The air suspension compressor assembly has the ability to detect faults and indicate the appropriate fault code via a blink code on the inflator switch LED. The air suspension compressor assembly will indicate the code when the condition that caused the code is current. In some instances the air suspension compressor assembly may set a flag that requires the ASCM to be reset. The ASCM will reset on its own after the ignition has been turned off for more than 2 1/2 hours or if the air suspension fuse has been removed with the ignition key turned off.

The air suspension sensor arm is attached to an armature that rotates inside a coil. The inductance of the coil, not the resistance, changes dependant on the position of the armature in the coil. The air suspension module determines the angle of the sensor arm by sending an inductive voltage through the coil and measuring the response time. The sensors must be calibrated to the correct D height.

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