ABS Description and Operation: Notes

This vehicle is equipped with an Advics HB-CI brake master cylinder assembly. The electronic brake control module (EBCM) and the brake pressure modulator valve (BPMV) is serviced as one assembly. 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)
• Hydraulic Brake Booster Power Supply
• Traction Control System (TCS) (w/NW7)
• Vehicle Stability Enhancement System (VSES) (w/JL4)

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

• ABS Pump Motor - The ABS pump motor is part of the hydraulic brake booster. The ABS pump motor is active during ABS, VSES and base brake power assist functions.
• Accumulator Pressure Sensor-The accumulator pressure sensor is located internally within the BPMV. The accumulator pressure sensor uses a 5-volt reference and generates an output signal proportionate to the hydraulic fluid pressure which is present in the accumulator.
• Backup Lamp Switch- On vehicles equipped with manual transmissions, the EBCM receives a voltage signal on the backup lamp supply voltage circuit when the vehicle is in reverse gear. The EBCM uses the backup lamp supply voltage circuit to enhance the operation of the ABS, VSES and TCS in reverse.
• Yaw Rate Sensor/Lateral and Longitudinal Accelerometer (w/JL4)-The EBCM uses the lateral and longitudinal accelerometers to determine the sideways and front to back acceleration of the vehicle. The Yaw rate sensor determines the vehicle rotation. The lateral accelerometer, yaw rate and longitudinal sensor are combined into one single component.
• Longitudinal Accelerometer (w/o JL4)-The EBCM uses the longitudinal accelerometer to determine the actual straight-line acceleration of the vehicle.
• 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.
• Steering Wheel Position Sensor (SWPS) (w/JL4)-The EBCM uses the SWPS as an indication of the position and rotation of the steering wheel.
• System relays-There are two system relays internal to the EBCM. The solenoid relay is energized when the ignition is ON. The ABS pump motor relay supplies battery positive voltage to the ABS pump motor when the EBCM commands the ABS pump motor on. The system relays are non serviceable.
• Traction Control Switch -Engine traction Control and 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.
• Stop Lamp Switch-The EBCM receives a voltage signal on the stop lamp supply voltage circuit when the brake pedal is applied. The EBCM applies a voltage to the center high mounted stop lamp (CHMSL) during a VSES event and sends a serial data message to the body control module (BCM) requesting stop lamp activation. The EBCM uses the stop lamp supply voltage circuit to enhance the operation of the ABS, VSES and TCS.