ABS Description and Operation: Notes

The vehicle is equipped with the following braking systems:

• Antilock Brake System (ABS)
• Dynamic Rear Proportioning (DRP)
• Vehicle Stability Enhancement System (VSES)

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

Electronic brake control module (EBCM) controls the system functions and detects failures.

The EBCM contains the following components:

• Internal pump relay-The relay is energized to supply B+ to the hydraulic pump.
• Solenoids-The solenoids are commanded by the EBCM to operate the appropriate valves in the brake pressure modulator valve.
• 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.
• The BPMV contains the following components:
  • Pump motor
  • Inlet valves (one per wheel)
  • Outlet valves (one per wheel)
  • Master cylinder isolation valves (one per drive wheel)
  • Prime valves (one per drive wheel)
• The wheel speed sensor receives B+ from the electronic brake control module (EBCM) and monitors the wheel speed by providing a DC square wave signal back to the module. As the wheel spins, the EBCM uses the frequency of the square wave signal to calculate the wheel speed.
• Stability control switch-The stability control can be manually disabled using the stability control switch.
• Stop lamp switch-The EBCM uses the stop lamp switch as an indication that the brake pedal is applied.
• Lateral accelerometer sensor-The EBCM uses the lateral accelerometer sensor as an indication of the lateral acceleration of the vehicle.
• Yaw rate sensor-The EBCM uses the yaw rate sensor as an indication of the yaw rate of the vehicle.
• Steering wheel position sensor (SWPS)-The EBCM uses the SWPS as an indication of the position and rotation of the steering wheel.