Anti-Lock Braking

The standard ABS module manages anti-lock braking to maintain vehicle control during deceleration.

The ABS module monitors and compares the rotational speed of each wheel. Wheel speeds are measured by the wheel speed sensor, which electrically senses each tooth of the sensor ring as it passes through the magnetic field of the sensor. When the ABS module detects an impending wheel lock, the ABS module commands the hydraulic pump motor on and commands the Hydraulic Control Unit (HCU) to open and close the appropriate solenoid valves to modulate the brake pressure to the individual brake caliper(s). Once the affected wheel(s) return to the desired speed, the ABS module commands the HCU to return the solenoid valves to their normal position and normal base brake operation is restored.

The ABS module is self-monitoring. When the ignition switch is in the RUN position, the ABS module does a preliminary electrical check and, at approximately 12 km/h (8 mph), the hydraulic pump motor is turned on for approximately one-half second. During this time a buzzing or humming noise may be heard and a vibration maybe felt in the brake pedal. This is a normal condition. If a malfunction is detected in the system, the module disables the ABS system and illuminates the yellow ABS warning indicator. However, the base power-assist braking system functions normally.