Suspension Control ( Automatic - Electronic ): Description and Operation

Vehicle Dynamic Suspension

The rear air suspension system is comprised of the following components:

- Message center
- Vehicle Dynamics Module (VDM)
- Two suspension ride height sensors
- Compressor and drier assembly (includes vent solenoid)
- Air tubes
- Rear air spring and shock absorber assemblies
- Two air spring solenoid valves
- Compressor relay


Air Suspension System Operation

The rear wheel air suspension system operates in the following manner:

- Vehicle height is controlled by the VDM.
- Each air spring has a solenoid that must open to vent (or compress).
- The air suspension compressor has a vent solenoid that must open to vent the system.
- The rear air springs raise or vent together.
- The system does not operate when:
- any of the doors are open.
- the liftgate or liftgate glass is open.
- the power running boards are deployed.

- The system will vent/compress when the vehicle speed exceeds 24 km/h (15 mph) even if the air suspension has been set to the OFF position.
- Trim height is normal driving height.
- The height sensor:
- system uses RH and LH rear height sensors.
- output voltage is between 0.5 and 4.5 volts.
- voltage output decreases (goes from high to low) as the suspension system raises the vehicle.

- The suspension ride height changes when:
- the key is in the ON position, the load leveling feature automatically makes adjustments to the vehicle height so that the vehicle is always at target height and constant front-to-rear vehicle attitudes are maintained over the load range of the vehicle.
- the key is in the OFF position. The system will remain active for 40 minutes after the ignition is turned off, allowing the system to deflate (vent) at any time while allowing the system to inflate (pump) only once at the end of 40 minutes.

Air Suspension Pneumatic Diagram