ABS Description and Operation: Notes

The vehicle may be equipped with the following braking systems:

• Antilock brake system (ABS)
• Electronic brake force distribution (EBD)
• Brake assist (BA)
• Traction control system (TCS)
• Vehicle stability enhancement system (VSES)

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

• Electronic brake control module (EBCM)-The EBCM controls the system functions and detects failures.
• 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.
  IMPORTANT: There is a rubber isolator located under the BPMV and on the mounting studs. The rubber isolators protect the BPMV and the EBCM from vehicle vibrations.

  The BPMV contains the following components:

  • Pump motor
  • Hold valves, one per wheel
  • Reduction Valves, one per wheel
  • Master cylinder valves
• Wheel speed sensors (WSS)-As the wheel spins, the wheel speed sensor produces an AC signal. The EBCM uses this AC signal to calculate wheel speed. The wheel speed sensors are replaceable only as part of the wheel hub and bearing assemblies.
• Traction control switch-The traction control system (TCS) is manually disabled or enabled using the traction control switch.
• Yaw rate/deceleration sensor -The EBCM uses the yaw rate/deceleration sensor as an indication of the yaw rate and lateral acceleration/deceleration of the vehicle.
• Steering angle sensor -The EBCM uses the steering angle sensor as an indication of the position and rotation of the steering wheel.
• Brake pressure sensor -The EBCM uses the brake pressure sensor for more accurate control during a VSES event.