System Operation

The air suspension switch, mounted in left side of trunk, is used to control system operation during diagnosis or repairs. The air suspension Vehicle Dynamics Module (VDM) maintains vehicle at a preset height, provides a soft ride for normal driving, and switches to a firm ride during hard braking, acceleration or cornering.

VDM reads height sensor travel every 5 milliseconds. Height sensors lengthen and shorten to respond to changes in road surface. 3 ride control settings are available. FIRM, NORMAL and PLUSH. Ride setting menu is selected through the Message Center by pressing RIDE/STEER button. Pressing SELECT button will cycle ride selections. Suspension will adjust to selection displayed when RIDE/STEER button is pressed to exit programming mode. Steering assistance is selected from same menu in the same manner. VDM automatically prevents selection of both HIGH steering assist and FIRM ride setting.

VDM will adjust suspension from PLUSH to NORMAL when vehicle exceeds 70 MPH (85 MPH on 1997 models) and to FIRM when speed exceeds 80 MPH (95 MPH on 1997 models). Ride control will adjust down again as vehicle speed decreases. VDM receives inputs from height sensors and controls air springs to maintain vehicle height. Additional control components are air spring solenoids, compressor motor, vent solenoid, and air compressor relay.

To raise vehicle, air suspension VDM first turns on air compressor through the air compressor relay. After a one-second delay, desired air spring solenoid is activated. Air compressor and air spring solenoid will remain on until air suspension VDM determines vehicle has obtained correct height through input signals from height sensors. Air suspension VDM will turn off air compressor and then close air spring solenoids.

To lower vehicle, air suspension control module opens vent solenoid on air compressor and opens solenoid valves. Vehicle will lower until correct height is obtained through input signals from height sensor. Air suspension VDM will then close vent and solenoid valves.

Air suspension system will operate for up to 30 minutes after ignition is turned off. During this interval, vent solenoid will operate as often as required. However, air compressor will operate only once.

Air suspension system will operate automatically when ignition is turned on. Battery voltage is provided through fuse No. 7 (No. 22 on 1997 models) to air suspension VDM. On all models, fuse is located in power distribution box and is a 30-amp fuse. VDM is located in trunk, behind package tray.

If air suspension switch is in OFF position with ignition switch in ON position, AIR LEVELING SYSTEM DISABLED will be displayed on message center. Message center is located on instrument panel, to right of steering column. If a system failure exists, CHECK RIDE CONTROL light will be displayed.