ABS Description and Operation: Notes

WARNING: This page is about a different car, the 2002 GMC Savana Special, 2002 GMC Savana Camper Special, 2002 GMC Savana, and 2002 Chevrolet Chevy Express. However, it is still accessible from the selected car via links, so may be relevant.

Fig 1: Electronic Brake Control Module

Courtesy of GENERAL MOTORS CORP.

Fig 2: BPMV Hydraulic Flow

Courtesy of GENERAL MOTORS CORP.

This vehicle is equipped with the EBC310 anti-lock braking system.

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

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 internal to the EBCM. The system relay is energized when the ignition is ON. The system relay supplies battery positive voltage to the solenoid valves and to the pump motor. This voltage is referred to as system voltage.
- Solenoids
  The solenoids are commanded On and OFF by the EBCM to operate the appropriate valves in the brake pressure modulator valve (BPMV).
Brake pressure modulator valve (BPMV)
The BPMV uses a 3-circuit configuration to control the left front wheel, the right front wheel, and the combined rear wheels. The BPMV directs fluid to the left front and right front wheels independently. The BPMV directs fluid to both of the rear wheels on a single hydraulic circuit.

The BPMV contains the following components:
- Pump motor
- Three isolation valves
- Three dump valves
- A front low-pressure accumulator
- A rear low-pressure accumulator
Wheel speed sensors (WSS)
As the front wheels spin, toothed rings located at each wheel hub interrupt magnetic fields in the wheel speed sensors. This causes each wheel speed sensor to generate an AC signal. The EBCM uses these AC signals to calculate the wheel speed. The wheel speed sensors are serviceable only as part of the wheel hub and bearing assemblies. Any imperfections in the toothed ring, such as a missing or damaged tooth, can cause an inaccurate WSS signal.
Vehicle speed sensor (VSS)
The input signal for rear wheel speed originates at the VSS. The powertrain control module (PCM) or vehicle speed sensor buffer (VSSB) receives rear wheel speed input from the VSS and supplies this information to the EBCM.