― If the ABS CM senses a wheel is about to lock, based on ABS wheel speed sensor data, it closes the normally open solenoid valve for that circuit. This prevents any more fluid from entering that circuit.
― The ABS CM then looks at the ABS wheel-speed sensor signal from the affected wheel(s) again.
― If that wheel(s) is still decelerating, it opens the closed solenoid valve for that circuit.
― Once the ABS-applied wheel comes back up to speed, the ABS CM returns the valves to their normal condition, allowing fluid to flow to the affected brake.
― The ABS CM monitors the electromechanical components of the system.
― A malfunction in the ABS system will cause the ABS CM to shut off or inhibit the system. However, normal power-assisted braking continues.
― Malfunctions are indicated by a yellow ABS warning light in the instrument cluster.
― The ABS system includes an on-board diagnostic function. When the ignition switch is turned to the ON position, the ABS CM performs a system self-diagnostic indicated by a 3 s illumination of the yellow ABS warning light and the red brake system warning light (if the parking brake is released).
― During vehicle operation, including normal and ABS braking, the ABS CM monitors all electrical anti-lock functions and some hydraulic operations.
― Each time the vehicle is driven, as soon as vehicle speed reaches approx. 20 km/h {12 mph}, the ABS CM turns on the pump motor for approx. 30 s. This is a normal function of the self-diagnostic by the ABS CM.
― Pedal pulsation coupled with noise while braking on loose gravel, bumps, wet or snowy roads is normal and indicates correct functioning of the vehicle’s ABS system.