Operation

The Anti-lock Brake System (ABS) and the traction control system consists of the following components:
- anti-lock brake control module
- Hydraulic Control Unit (HCU)
- rear anti-lock brake sensors
- rear anti-lock brake sensor indicators
- front anti-lock brake sensors
- front anti-lock brake sensor indicators
- vehicle message center
- yellow ABS warning indicator
- yellow TRAC OFF indicator

WARNING: Brake fluid contains POLYGLYCOLETHERS AND POLYGLYCOLS. Avoid contact with eyes. Wash hands thoroughly after handling. If brake fluid contacts eyes, flush eyes with running water for 15 minutes. Get medical attention if irritation persists. If taken internally, drink water and induce vomiting. Get medical attention immediately.

The ABS operates as follows:
- When the brakes are applied, fluid is forced from the brake master cylinder outlet ports to the brake pressure control valve block inlet ports. This pressure is transmitted through four normally open solenoid valves contained inside the brake pressure control valve block and then through the outlet ports of the brake pressure control valve block to each wheel.
- The primary (rear) circuit of the brake master cylinder feeds the right front and left rear brakes.
- The secondary (front) circuit of the brake master cylinder feeds the left front and right rear brakes.
- If the anti-lock brake control module senses a wheel is about to lock, based on brake anti-lock sensor data, it closes the normally open solenoid valve for that circuit. This prevents any more fluid from entering that circuit.
- The anti-lock brake control module then looks at the brake anti-lock sensor signal from the affected wheels again. If that wheel is still decelerating, it opens the closed solenoid valve for that circuit.
- Once the affected wheel comes back up to speed, the anti-lock brake control module returns the valves to their normal condition, allowing fluid to flow to the affected brake.
- Any malfunction of the anti-lock brake system will cause the anti-lock brake control module to shut off or inhibit the system. However, normal power-assisted braking remains.
- The 4-wheel ABS is self-monitoring. When the ignition switch is turned to the RUN position, the anti-lock brake control module will perform a preliminary self-check of the anti-lock electrical system indicated by a three-second illumination of the yellow ABS warning indicator in the instrument cluster.
- During vehicle operation, including normal and anti-lock braking, the anti-lock brake control module monitors all electrical anti-lock functions and some hydraulic operations.
- Each time the vehicle is driven, as soon as vehicle speed reaches approximately 20 km/h (12 mph), the anti-lock brake control module turns on the pump motor for approximately one-half second. At this time, a mechanical noise may be heard. This is a normal function of the self-check by the anti-lock brake control module.
- For most malfunctions of the anti-lock brake with traction control system, the yellow ABS warning indicator will be illuminated.