ABS Description and Operation: Notes

This vehicle is equipped with the MK 25 E Continental Teves antilock braking system.

The vehicle is equipped with the following braking systems:

• Antilock Brake System (ABS)
• Engine Drag Control (EDC)
• Electronic Brake Distribution (EBD)
• 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.

  The EBCM contains the following components:

  • Motor Relay-The motor relay is energized when the ignition is ON and no ABS DTCs are present. It supplies battery positive voltage to the pump motor.
  • Valve Relay-The valve relay is energized when the ignition is ON and no ABS DTCs are present. It supplies battery positive voltage to the solenoid valves.
• 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
  • Inlet Valves (one per wheel)
  • Outlet Valves (one per wheel)
  • Master Cylinder Isolation Valves (one per drive wheel)
• The wheel speed sensor receives a 12-volt power supply voltage from the electronic brake control module (EBCM) and provides an output signal to the EBCM. As the wheel spins, the wheel speed sensor sends the EBCM a DC square wave signal. The EBCM uses the frequency of the square wave signal to calculate the wheel speed.
• Traction Control Switch - The TCS is manually disabled or enabled using the traction control switch.
• Brake Pedal Position - The EBCM uses the BPP sensor 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 Angle Sensor (SAS) - The EBCM uses the SAS as an indication of the position and rotation of the steering wheel.