The hydraulic pump maintains a pressure between 14,000 kPa (2030 psi) and 18,000 kPa (2610 psi) in the accumulator and is connected by a high-pressure hose to the booster chamber portion of the hydraulic actuation assembly and a control valve. When the brakes are applied, a scissor-lever mechanism activates the control valve and a pressure, proportional to the pedal travel, enters the booster chamber portion of the hydraulic actuation assembly. This pressure is transmitted through the normally open solenoid valve through the proportioning valve to the rear brakes. The same pressure moves the booster piston against the master cylinder piston, shutting off the central valves in the master cylinder. This applies pressure to the front wheels through the two front, normally open, solenoid valves.
The electronic controller monitors the electromechanical components of the system. Malfunction of the anti-lock brake system will cause the electronic controller to shut off or inhibit the anti-lock feature in the brake system. However, normal power assisted braking remains. Malfunctions are indicated by one or two warning indicators inside the vehicle.
Loss of hydraulic fluid or power boost pressure will inhibit the anti-lock brake system.
The 4-wheel anti-lock brake system is self-monitoring. When the vehicle ignition switch is placed in the RUN position, the electronic controller will perform a preliminary self check on the anti-lock electrical system indicated by a three to four second illumination of the amber Check Anti-Lock Brakes indicator in the instrument cluster. It is possible that both the CHECK ANTI-LOCK BRAKE and BRAKE warning indicators will stay lit for up to 60 seconds after the ignition is placed in the RUN position, while the pump runs to fully charge the accumulator. During vehicle operation, including normal and anti-lock braking, the electronic controller monitors all electrical anti-lock functions and some hydraulic operations.
In most malfunctions in the anti-lock brake system, the amber "CHECK ANTI-LOCK BRAKES" and/or "BRAKE" indicator will be illuminated. The sequence of illumination of these warning indicators combined with the symptoms can determine the appropriate diagnostic tests to perform. However, most malfunctions are recorded as a coded number in the controller memory and pinpoint the component needing service.