Base ABS

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

When the ignition switch is in the RUN position, the ABS module does a preliminary electrical check and, at approximately 12 km/h (7 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 may be felt in the brake pedal. This is a normal condition. Any malfunction of the ABS disables the ABS function and the ABS warning indicator illuminates. However, the power-assist braking system functions normally.

The ABS module continuously monitors and compares the rotational speed of each wheel. This is accomplished using 4 active wheel speed sensors, one for each wheel. The wheel speed sensors are connected to the ABS module by 2 circuits. One circuit provides voltage for sensor operation and the other circuit provides sensor input to the ABS module. As the wheels spin, the wheel bearing magnetic strip passes through the magnetic field generated by the active wheel speed sensor. This creates a square-wave signal that is sent to the ABS module to indicate individual wheel speed. When the ABS module detects an impending wheel lock, the ABS module commands the hydraulic pump motor on and 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, restoring normal base brake operation.