Check Height sensor
Check for Air Leaks
Apply a soapy water solution to the air lines, air line fittings, air springs, upper spring shock mount and the air compressor
The 4-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 liftgate 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 in) 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 in) 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.
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, the doors and liftgate are closed 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 liftgate are CLOSED, ride height changes from kneel to trim.
The 4x4 system mode is switched to 4x4 low, the ride height changes to off-road.