ABS Description and Operation: Notes

This vehicle is equipped with an TRW 440 brake master cylinder assembly. The electronic brake control module (EBCM) and the brake pressure modulator valve (BPMV) can be serviced separately. The BPMV uses a 4-circuit configuration to control hydraulic pressure to each wheel independently.

The following vehicle performance enhancement systems are provided.

• Antilock Brake System (ABS)
• Dynamic Rear Proportioning (DRP)
• Traction Control System (TCS) (w/NW7)

The following components are involved in the operation of the above systems:

• Brake pressure modulator valve (BPMV)-The BPMV contains the hydraulic valves and pump motor that are controlled electrically by the EBCM. The BPMV uses a 4-circuit configuration with a diagonal split. The BPMV directs fluid from the reservoir of the master cylinder to the left front and right rear wheels and fluid from the other reservoir to the right front and left rear wheels. The diagonal circuits are hydraulically isolated so that a leak or malfunction in one circuit will allow continued braking ability on the other.
• Master cylinder pressure sensor-The master cylinder pressure sensor is located within the BPMV. The master cylinder pressure sensor uses a 5-volt reference and generates an output signal proportionate to the hydraulic fluid pressure which is present in the hydraulic brake circuit at the master cylinder.
• Solenoids-The solenoids are commanded ON and OFF by the EBCM to operate the appropriate valves in the BPMV.
• System relay-There are 2 system relays internal to the EBCM. The system relays are energized when the ignition is ON. The system relays supply battery positive voltage to the valve solenoids and to the ABS pump motor. This voltage is referred to as system voltage
• Traction control switch (w/NW7 and w/JL4)-TCS and vehicle stability enhancement system (VSES) is manually disabled or enabled using the traction control switch.
• Wheel speed sensors (WSS)-EBCM sends a 12-volt reference voltage signal to each wheel speed sensor. As the wheel spins, the wheel speed sensor produces a square wave DC signal voltage. The wheel speed sensor increases the signal frequency as the wheel speed increases, but does not increase the signal amplitude.
• Brake pedal position (BPP) sensor-The EBCM receives a serial data message from the body control module (BCM) to indicate that the brake pedal is applied.