Test K: Poor Vehicle Tracking During Abs Operation

Bleed brake System

Bleed brake system. See BLEEDING BRAKE SYSTEM . If vehicle still does not track properly, go to next go to next step. If vehicle tracks properly after bleeding brakes, problem is corrected.

Check Left Front ABS Inlet Valve (Closed Position)

Raise and support vehicle. Rotate all 4 wheels to ensure free rotation. Turn ignition on. Using scan tool, trigger ABS control module active command LF INLET ON. Moderately apply brake pedal. Have an assistant attempt to rotate left front wheel. If wheel rotates, trigger active command LF INLET OFF and go to next step. If wheel does not rotate, replace HCU. Clear codes and repeat self-test.

Check Left Front ABS Inlet Valve (Open Position)

While rotating left front wheel, moderately apply brake pedal. If left front wheel rotates, replace HCU. Repeat self-test. If left front wheel does not rotate, go to next step.

Check Left Front ABS Output Valve (Open Position)

Apply moderate brake pedal. Using scan tester, command LF INLET ON. Command ABS POWER ON for 6 seconds. Trigger must be depressed 3 times. Each press runs pump for 2 seconds. Command ABS control module LF OUTLET, ON and then OFF 3 times. With help from an assistant, attempt to rotate left front wheel. If wheel does not rotate, replace HCU. Repeat self-test. If wheel rotates, trigger all active commands OFF and go to next step.

Check Left Front ABS Outlet Valve (Closed Position)

Apply moderate brake pedal effort. With help from an assistant attempt to rotate left front wheel. If wheel rotates, replace HCU. Repeat self-test. If wheel does not rotate, repeat test from step 2 for RF, LR and RR wheels using commands specified. If no failure occurs, the system is operating normally.