Initial Inspection and Diagnostic Overview
Inspection and Verification1. Verify the customer concern.
2. NOTE: If the door ajar indicator is illuminated when all doors, liftgate, and liftgate glass are closed, the air suspension will not work correctly. Repair door ajar indicator.
Visually inspect for obvious signs of mechanical and electrical damage.
Visual Inspection Chart
3. If the inspection reveals an obvious concern that can be readily repaired, correct the concern before continuing with Inspection and Verification.
4. If the concern remains after the inspection, use the scan tool connected to the Data Link Connector (DLC) to retrieve continuous diagnostic trouble codes (DTCs) and to execute On-Demand Self-Test diagnostics for the 4WAS module.
^ If the On-Demand Sell: Test is passed and no DTCs are retrieved, GO to Symptom Chart to continue diagnostics Symptom Related Diagnostic Procedures.
^ If DTCs are retrieved, go to the 4WAS Module Diagnostic Trouble Code (DTC) Index. Diagnostic Trouble Code Tests and Associated Procedures
^ If the 4WAS module cannot be accessed by the scan tool, GO to Pinpoint Test A. Test A
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 properly. Verify that the following conditions are met before running the Pneumatic Test.
^ All doors, liftgate, and liftgate glass must be closed.
^ Vehicle in PARK.
^ The vehicle speed is less the 3 km/h (1.87 mph).
^ The air suspension service switch must be in the ON position.
^ Test is used to clear DTCs C1990 and C1991.
Trim Height Test
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.
^ All doors, liftgate, and liftgate glass must be closed.
^ The transmission is in PARK.
^ The vehicle speed is less than 3 km/h (1.87 mph).
^ The ignition switch is in the ON position.
^ The air suspension service switch is in the ON position.
^ Battery voltage greater than 11 volts for duration of test.
1. Fulfill the preconditions.
2. Install a battery charger for the Trim Height Test to prevent battery drain.
3. Run the Trim Height Test.
Self-Test
Verify that the following conditions are met before running the On-Demand Self-Test.
^ All doors, liftgate, and liftgate glass must be closed.
^ The transmission is in PARK.
^ The vehicle speed is less than 3 km/h (1.87 mph).
^ The ignition switch its in the 0N position.
^ The vehicle is not in 4L mode.
1. Fulfill the preconditions.
2. Install a battery charger for the On-Demand Self-Test to prevent battery drain.
3. Run the air suspension On-Demand Sell Test.
4. Record all listed DTCs.
5. Retrieve stored DTCs.
6. Troubleshoot any On-Demand Sell Test DTCs first.
7. Repeat the ON-Demand Sell Test and clear DTCs after repairs are completed.