ABS Description And Operation: Notes

Fig 1: BPMV And EBCM

Courtesy of GENERAL MOTORS CORP.

Fig 2: BPMV Hydraulic Flow

Courtesy of GENERAL MOTORS CORP.

This vehicle is equipped with the Bosch 5.3 anti-lock braking system.

The vehicle is equipped with the following braking systems:

• Anti-lock Brake System (ABS)
• Dynamic Rear Proportioning (DRP)
• Traction Control System (TCS) (w/NW9)
• 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:

  • System Relay, The system relay is energized when the ignition is ON and no ABS DTCs are present. It supplies battery positive voltage to the solenoid valves and pump motor.
  • Vent Tube, The vent tube, located in the EBCM connector, is an opening to the internal cavity of the EBCM. It allows ventilation of the EBCM internals.
• 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 (w/NW9), one per drive wheel
  • Prime Valves (w/NW9), one per drive wheel
• 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 (w/NW9) - The TCS is manually disabled or enabled using the traction control switch.
• Stoplamp Switch - The EBCM uses the stoplamp switch as an indication that the brake pedal is applied.
• Lateral Accelerometer Sensor (w/JL4), the EBCM uses the lateral accelerometer sensor as an indication of the lateral acceleration of the vehicle.
• Yaw Rate Sensor (w/JL4), The EBCM uses the yaw rate sensor as an indication of the yaw rate of the vehicle.
• Steering Wheel Position Sensor (SWPS) (w/JL4), The EBCM uses the SWPS as an indication of the position and rotation of the steering wheel.
• Brake Pressure Sensor (w/JL4), The EBCM uses the brake pressure sensor for more accurate control during a VSES event.