Test I: Poor Vehicle Tracking During Anti-Lock Function
- Turn air suspension switch off. Switch is located in left side of luggage compartment. Connect NGS tester or scan tool. Turn ignition switch to RUN position. Raise vehicle of hoist until wheels are off ground. Check that all wheels rotate freely (transmission in Neutral and parking brake off). Trigger ABCM active command PMP MOTOR ON for 4 seconds (push trigger twice; each triggering runs pump for 2 seconds). Apply moderate brake pedal. Have assistant attempt to rotate LF wheel. If LF wheel rotates, install new HCU. Restore vehicle, clear DTCs and retest system. If wheel does not rotate, go to next step.
- Trigger ABCM active command mode LF INLET ON and LF OUTLET ON. Have assistant turn LF wheel, using a long-handle breaker bar, immediately after triggering ABCM. If LF wheel turns, go to next step. If LF wheel does not turn, go to step 9.
- Turn ignition switch to RUN position. Trigger ABCM active command PMP MOTOR ON for 4 seconds (push trigger twice; each time pump will run for 2 seconds). Apply moderate brake pedal. Have assistant try to turn RF wheel. If RF wheel turns, replace HCU. Restore vehicle, clear DTCs and retest system. If RF wheel does not turn, go to next step.
- Trigger ABCM active command RF INLET ON and RF OUTLET ON. Have assistant turn RF wheel, using a long-handle breaker bar, immediately after triggering ABCM. If RF wheel turns, go to next step. If RF wheel does not turn, go to step 9.
- Trigger ABCM active command PMP MOTOR ON for 4 seconds (push trigger twice; each triggering runs pump for 2 seconds). Apply moderate brake pedal. Have assistant attempt to rotate left rear wheel. If left rear wheel rotates, install new HCU. Restore vehicle, clear DTCs and retest system. If left rear wheel does not rotate, go to next step.
- Trigger ABCM active command mode LR INLET ON and LR OUTLET ON. Have assistant turn left rear wheel, using a long-handle breaker bar, immediately after triggering ABCM. If left rear wheel turns, go to next step. If left rear wheel does not turn, go to step 9.
- Trigger ABCM active command PMP MOTOR ON for 4 seconds (push trigger twice; each triggering runs pump for 2 seconds). Apply moderate brake pedal. Have assistant attempt to rotate right rear wheel. If right rear wheel rotates, install new HCU. Restore vehicle, clear DTCs and retest system. If right rear wheel does not rotate, go to next step.
- Trigger ABCM active command mode RR INLET ON and RR OUTLET ON. Have assistant turn right rear wheel, using a long-handle breaker bar, immediately after triggering ABCM. If right rear wheel turns, ABS system is operating properly. Restore vehicle, clear DTCs and retest system. If right rear wheel does not turn, go to next step.
- Retrieve and document any continuous DTCs. If any DTCs are retrieved, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no DTCs are retrieved, install new HCU. Restore vehicle, clear DTCs and retest system.