Anti-Lock Brake System (ABS) with Traction Control
The anti-lock brake system consists of the following components:
Principles of Operation
The anti-lock brake system (ABS) module receives wheel speed readings from each wheel speed sensor and processes this information to determine if an ABS event is necessary. The wheel speed sensor electrically senses each tooth of the wheel speed sensor indicators as it passes through the wheel speed sensor's magnetic field.
The ABS module continuously monitors and compares the rotational speed of each wheel, and when it detects an impending wheel lock, modulates hydraulic brake pressure to the appropriate brake caliper. This is accomplished by the ABS module triggering the hydraulic control unit (HCU) to open and close the appropriate solenoid valves. Once the affected wheel returns to normal speed, the ABS module returns the solenoid valves to their normal position, and normal (base) braking resumes.
The ABS module is self-monitoring. When the ignition switch is turned to the RUN position, the ABS module does a preliminary electrical check, and at approximately 12 km/h (8 mph) the pump motor is turned on for approximately one half-second. Any malfunction of the ABS causes the ABS to shut off and the yellow ABS warning indicator to illuminate, however, normal power assisted braking remains.
The traction control system controls wheel spin by modulating engine torque and applying, then releasing the appropriate rear brake to restore traction when driving on slippery or loose surfaces.
The traction control system can be disabled by pressing the traction control switch and is indicated by an indicator lamp in the traction control switch. The traction control will reset and return to normal traction assist when the ignition switch is cycled or when the traction control switch is pressed and released a second time.