Anti-Lock Brake System: Description
The Anti-Lock Brake System (ABS) consists of an ABS Electronic Control Unit (ECU), hydraulic brake booster (master cylinder and actuator combination), 4 wheel-speed sensors, deceleration sensor and stoplight switch. See Fig 1.
The ABS indicator light is located on the instrument panel. This light illuminates for 3 seconds as a bulb test when ignition is first turned on. A primary check is performed after each engine start, and initial vehicle speed exceeds 4 MPH. If brake pedal is pressed before vehicle exceeds 4 MPH, primary check will not occur until brake pedal is released.
Under normal driving conditions, the ABS functions as a standard brake system. With detection of wheel lock-up, short pedal pulsations occurring in rapid succession will be felt in brake pedal. Pedal pulsation will continue until there is no longer a need for ABS function.