The Anti-lock Brake System (ABS) available on 1993 and later 80 series vehicles is designed to maintain vehicle steerability, directional stability, and optimum deceleration under severe braking conditions and on most road surfaces by monitoring the rotational speed of each wheel and controlling brake line pressure to prevent wheel lock-up. The actuator assembly includes the master cylinder, an electric hydraulic pump, and four solenoid valves, with the pump providing hydraulic pressure to charge the reservoirs that supply pressure to the braking system. Speed sensors located at each wheel generate electrical pulsations to indicate wheel rotational speed, with front sensors mounted to the steering knuckle and rear sensors bolted to the axle carriers. The ABS computer, mounted under the dashboard, processes information from the wheel speed sensors to control hydraulic line pressure and monitors the system for faults, illuminating an "ABS" light on the dashboard if a problem develops. The ABS system control unit features a self-diagnosis system that detects sensor malfunctions and alerts the driver through the ABS warning light, which should turn off when the engine starts unless a malfunction is present. Diagnostic codes can be accessed by turning the ignition key to the ON position and using a jumper wire to connect specific terminals in the data link connector, with the ABS light indicating the number of flashes corresponding to the diagnostic code. The accompanying tables and charts provide details on the codes for various malfunctions, and after diagnosis, trouble codes can be cleared by depressing the brake pedal multiple times, followed by removing the jumper wire and reinstalling the connector cap, with further action recommended if issues persist.
