Vehicle Dynamic Suspension
Vehicle Dynamic SuspensionWARNING: The service switch for the air suspension system must be shut off prior to hoisting, jacking or towing an air suspension vehicle. This can be accomplished by turning off the air suspension switch located in the rear storage area in the rear of the passenger compartment. Failure to do so may result in unexpected inflation or deflation of the air springs which may result in shifting of the vehicle during these operations.
WARNING: Do not remove an air spring under any circumstances when there is pressure in the air spring. Do not remove any components supporting an air spring without either exhausting the air or providing support for the air spring to prevent vehicle damage or personal injury.
The four wheel air suspension system is comprised of the following components:
^ Service switch
^ Control module
^ Two front height sensors
^ One rear height sensor
Compressor and drier assembly (includes vent solenoid)
^ Air lines
^ Front and rear air spring and shock absorber assemblies
^ Four air spring solenoids
^ Compressor relay
Air Suspension System Operation
Air Suspension Pneumatic Diagram
The four-wheel air suspension system operates in the following manner:
^ Vehicle height is controlled by the 4-wheel air suspension module (vehicle dynamics module (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 transition from trim height to kneel height or from kneel height to trim height takes approximately 30 to 45 seconds.
^ The front air springs raise or vent independently.
^ The rear air springs raise or vent as a pair.
^ The system does not operate when:
- any of the doors are open.
- the liftgate or litigate glass is open.
- the power running boards are deployed.
^ The system will vent when the vehicle speed exceeds 24 Km/h (15 mph) even if the air suspension switch is in the OFF position.
^ Kneel mode is defined as 25 mm (0.98 inch) below trim height.
^ Trim height is normal driving height.
^ 4x4 off-road mode is engaged when the vehicle 4x4 system operates in 4x4 low mode at a speed of less than 30 Km/h (19 mph), and is defined as 25 mm (0.98 inch) above trim height.
^ Height sensor:
- The system uses 3 height sensors LF, RF and rear.
- Height sensor output voltage is between 0.5 and 4.5 volts or 0 to 5 volts.
- The LF and RF have opposite electrical polarities.
- Height sensor voltage output decreases (goes from high to low) as the suspension system raises.
^ The suspension ride height changes when:
- the ignition key is in the RUN position and the vehicle is shifted to DRIVE or REVERSE, ride height changes from kneel to trim.
- the ignition key is in the OFF position, the doors and litigate are closed then opened, ride height changes from kneel to trim.
- the 4x4 system mode is switched to 4x4 low, the ride height changes to off-road.