Principles of Operation
Principles of OperationWARNING: Before repairing or installing any air suspension component(s), turn off the air suspension switch or disconnect the battery ground cable to prevent vehicle damage or personal injury.
WARNING: Do not attempt to install or inflate any air spring that has become unfolded to prevent vehicle damage or personal injury.
WARNING: Failure to observe the following procedures can result in a sudden failure of the suspension system.
WARNING: Any air spring which is unfolded must be refolded prior to being installed in a vehicle.
WARNING: The air spring refolding procedure should not be used for an air spring which has never supported the vehicle's weight while in the correctly folded position.
WARNING: Vehicles with an incorrectly folded air spring(s) found after the vehicle has been driven, must have a new air spring installed.
WARNING: Do not attempt to inflate any air spring which has collapsed while deflated from the rebound hanging position to the jounce stop.
WARNING: When installing a new air spring, care must be taken to not apply a load to the suspension until the air springs have been inflated using the air spring fill procedure.
WARNING: After inflating an air spring in the hanging position, it must be inspected for correct shape.
The air suspension system is designed to improve ride handling and general vehicle driving performance.
Rear Air Suspension Control Module
CAUTION: Before diagnosing the rear air suspension system, carry out the RAS module self-test. If a DTC is present, follow the diagnosis and testing procedures. If no DTC is present, check the vehicle ride height by following the ride height adjustment procedure.
If the system cannot reach the correct ride height, check all of the air supply lines and connections for leaks/blockage/or damage, height sensor integrity, and/or compressor relay operation before installing a new air compressor.
A microprocessor controls the air suspension system. The microprocessor and its supporting hardware are contained in the rear air suspension control module. The rear air suspension control module responds to signals from various sensors in the vehicle to maintain the programmed ride height while the vehicle is either moving or stopped. The rear air suspension control module accomplishes this by opening and closing solenoid valves to control the amount of air in the air spring(s). The rear air suspension control module turns on the compressor by applying voltage through the compressor relay to inflate the air spring(s) and raise the vehicle. The rear air suspension control module opens the vent solenoid to lower the vehicle by releasing air from the air spring(s) in response to signal inputs from the air suspension height sensor.
The air suspension module has a preprogrammed trim height. Whenever a door is opened, the air suspension will compensate in order to bring the vehicle back to the preprogrammed trim height.
Air Suspension Switch
CAUTION: The air suspension switch must be turned to the OFF position when the vehicle is hoisted, jacked, towed, jump started, or raised off the ground, to avoid unnecessary operation of the system and possible damage to the air suspension system components.
The air suspension switch provides a signal to the rear air suspension control module in the ON position to activate the system to maintain the programmed vehicle height.
Air Compressor
NOTE: The compressor contains a thermal overload circuit breaker. The circuit breaker automatically resets after a cool-down period and after being tripped by excessive compressor motor heat.
The air compressor assembly consists of the compressor pump, electric motor and vent solenoid (must be installed as an assembly).
Air Suspension Rotary Height Sensor
One air suspension height sensor is mounted on the vehicle. The air suspension height sensor sends a voltage signal to the air suspension control module. The output ranges from approximately 4.75 volts at minimum height (when the vehicle is low or in full jounce) to 0.25 volts at maximum height (when the vehicle is high or in full rebound). Install a new air suspension height sensor as a unit.
When the air suspension height sensor indicates that the rear of the vehicle is lower than trim height under normal driving conditions, the air compressor will turn on and pump compressed air into the air springs. When the sensor indicates that the rear of the vehicle is raised above trim under normal driving conditions, this will cause the air to be vented from the air springs to lower the vehicle back to its trim height level.
Solenoid Valve, Air Spring
WARNING: Never rotate an air spring solenoid valve to the release slot in the air spring end cap fitting until all pressurized air has escaped from the air spring.
The air spring solenoid valve allows air to enter and exit the rear air springs during height adjustment operations. The air spring solenoid valve is electrically operated and controlled by the air suspension control module.