On-Vehicle Inspection
- Ensure all diagnostic trouble codes have been cleared and battery is fully charged. See CLEARING CODES under DIAGNOSIS & TESTING. Turn ignition on and check if ABS warning light goes out after 2-4 seconds. If ABS warning light remains illuminated, ABS control module has detected a failure and will not activate hydraulic unit. See DIAGNOSIS & TESTING .
- Turn ignition off. Ensure vehicle is on level surface. Raise and support vehicle. Place transmission in Neutral. Release parking brake. Rotate wheels by hand and check for brake drag. Connect a jumper wire between TBS terminal and GND terminal of data link connector. See Figure . Depress brake pedal and have an assistant attempt to rotate right front wheel. Wheel should not rotate.
- With brake pedal still depressed, turn ignition on. Brake should be momentarily released (about .5 second) and wheel should turn when pressure reduction operates. Check operation of remaining wheels using same procedure beginning with left front, right rear, then left rear wheels.
- If all wheels operate as specified, the following systems are operating properly.
- Brake piping to hydraulic unit.
- Braking system, including hydraulic unit.
- Hydraulic unit electrical system (solenoid, pump motor, etc.)
- ABS control module output system (solenoid, relay, etc.) and harness.
- If all wheels do not operate as specified, check ABS control module input system and wiring harness for intermittent failure. Check for fluid leakage. Repair as necessary. If input system, wiring harness, intermittent failure or fluid leakage are not present, replace hydraulic unit.