ABS Description and Operation: Notes

Fig 1: EBCM and BPMV

Courtesy of GENERAL MOTORS CORP.

Fig 2: BPMV Hydraulic Flow

Courtesy of GENERAL MOTORS CORP.

This vehicle is equipped with the UBC7 antilock braking system.

The vehicle is equipped with the following braking systems:

• Antilock Brake System (ABS)
• Dynamic Rear Proportioning (UHP)

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

• Electronic Brake Control Module (EBOM)

  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.

  The BPMV contains the following components:

  • The Pump Motor
  • One Inlet Valve per wheel
  • One Outlet Valve per wheel
• The 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.

• The Stop Lamp Switch - The EBCM uses the stop lamp switch as an indication that the brake pedal is applied.