Inspection and Verification

Inspection and Verification
1. Verify the customer concern.

2. NOTE: If the door ajar indicator is illuminated when all doors, the liftgate and the liftgate glass are closed, the air suspension will not work correctly. Repair the door ajar indicator. Refer to Instrument Panel, Gauges and Warning Indicators.

Visually inspect for obvious signs of mechanical and electrical damage.

Visual Inspection Chart:

Visual Inspection Chart

3. If an obvious cause for an observed or reported concern is found, correct the cause (if possible) before proceeding to the next step.

4. NOTE: The VDM is also referred to as the 4-wheel air suspension (4WAS) module.

If the cause is not Visually evident, connect the diagnostic tool to the data link connector (DLC) to retrieve continuous diagnostic trouble codes (DTC's) and to execute On-Demand Self Test diagnostics for the VDM.
^ If the On-Demand Self Test is passed and no DTC's are retrieved, GO to Symptom Chart to continue diagnostics. Symptom Related Diagnostic Procedures
^ If DTC's are retrieved, GO to the VDM Diagnostic Trouble Code (DTC) Index. Diagnostic Trouble Code Tests and Associated Procedures
^ If the VDM cannot be accessed by the diagnostic tool, GO to Pinpoint Test A. Test A: No Communication With the Air Suspension Control Module

Pneumatic Test
This test verifies that the air lines are connected and that they are not restricted. It also verifies that the air compressor, air compressor vent solenoid and air spring solenoid valves are functioning correctly. Verify that the following conditions are met before running the Pneumatic Test.
^ All doors, the liftgate and the liftgate glass must be CLOSED.
^ Vehicle in PARK.
^ The vehicle speed is less the 10 km/h (6 mph).
^ The air suspension service switch must be in the ON position.
^ Test is used to clear DTC's C1990 and C1991.

Trim Height Test (or Accurate Trim Test)

NOTE: The trim height test is used to verify trim height only. If trim height needs to be adjusted, refer to Ride Height Adjustments.

The trim height test is used to make the vehicle level to within 2 mm (0.08 inch) of the calibrated trim height. Accurate trim test should be run before setting vehicle alignment.
The following conditions must be met for the trim height test to ran:
^ All doors, the liftgate and the liftgate glass must be CLOSED.
^ The transmission is in PARK.
^ The vehicle speed is less than 10 km/h (6 mph).
^ The ignition switch is in the ON position.
^ The air suspension service switch is in the ON position.
^ Battery voltage is greater than 11 volts for the duration of the test.

1. Fulfill the pre-conditions.
2. Install a battery charger for the Trim Height Test to prevent battery drain.
3. Using the diagnostic tool, run the Trim Height Test.

Self-Test
Verify that the following conditions are met before running the On-Demand Self Test.
^ All doors, the liftgate and the liftgate glass must be CLOSED.
^ The transmission is in PARK.
^ The vehicle speed is less than 10 km/h (6 mph).
^ The ignition switch is in the ON position.
^ The vehicle is not in 4L mode.

1. Fulfill the pre-conditions.
2. Install a battery charger for the On-Demand Self Test to prevent battery drain.
3. Run the air suspension On-Demand Self Test.
4. Record all listed DTC's.
5. Retrieve stored DTC's.
6. Troubleshoot any On-Demand Self Test DTC's. first.
7. Repeat the On-Demand Self Test and clear DTC's after repairs are completed.