A: Air Suspension System Overview

1. Vehicle height is controlled by the 4-Wheel Air Suspension Module (4WAS) based on height sensor output voltages.

2. The Vehicle Dynamics Module (VDM) and the 4-Wheel Air Suspension Module (4WAS) are the same module. This was a naming convention change in mid-model year 2003.

3. Each air spring has a solenoid that must open to vent or compress.

4. The air suspension compressor has a vent solenoid that must open to vent the system.

5. The transition from trim height to kneel height or from kneel height to trim height takes approximately 30 to 45 seconds.

6. The front air springs are independently controlled. The rear air springs are always controlled as a pair.

7. The system will not operate with any doors open, with the liftgate open, with the liftgate glass open or with the power running boards extended.

8. The air suspension switch position is ignored above 15 mph. The air suspension will be active over 15 mph, regardless of the switch position.

9. Kneel Mode is defined as 25 mm below Trim Mode.

10. Trim Mode is defined as normal driving height.

11. 4X4 Off-Road Mode is engaged when the vehicle is in 4X4 Low at a speed of less than 19 MPH, and is defined as 25 mm above trim height.

12. Height Sensor Operation

^ There are 3 height sensors - Left Front, Right Front, and Right Rear.

^ The sensor output ranges between 0.5 volts and 4.5 volts.

^ The Left Front and Right Front sensors are opposite in polarity.

^ The voltage output of the sensors decreases as the vehicle body rises and increases as the vehicle body lowers.

13. Ride Height Change Triggers

^ When the ignition key is in the "Run" position and the vehicle is shifted to either "Drive" or "Reverse", the ride height will change from Kneel to Trim.

^ When the ignition key is in the "Off" position and the doors are closed after being open, the ride height will change from Trim to kneel.

^ When the vehicle is engaged into 4X4 LOW, the ride height will change to Off-Road.