Antilock Brakes / Traction Control Systems: Description and Operation

The four wheel anti-lock brake system on these models is a compact integral power brake system that uses brake fluid for both brakeing function and anti-lock functions. This system is divided into three systems circuits with individual front brake circuits and combined rear brake circuit.
Accumulator pressure is maintained between 2030 and 2610 psi by the hydraulic pump, which is connected by a high pressure line to the booster chamber and a control valve. When the brakes are applied, the control valve is activated and a pressure, proportional to pedal travel, enters the booster chamber. This pressure travels through the normally open solenoid valve through the proportioning valve to the rear brakes. The same pressure also moves the booster piston against the master cylinder piston, shutting off the central valves in the master cylinder and applying pressure to the front wheels through the two front normally open solenoid valves.
The electronic controller monitors the electro-mechanical components of the system. A system malfunction will cause the controller to shut off or inhibit anti-lock brake control, while maintaining normal power assisted braking. Malfunctions are indicated by one or two indicator lamps inside the vehicle.The anti-lock brake system is self-monitoring. When the ignition switch is placed in the the Run position, the electronic controller will perform a preliminary self check on the electrical system indicated by a 3---4 second illumination of the ``Check Anti-Lock Brakes'' indicator lamp in the overhead console or instrument cluster. The electronic controller continues to monitor all electrical and many hydraulic anti-lock functions under all operating conditions.