ABS Description and Operation (Over 8600 GVW or PHT): Notes
WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
This vehicle is equipped with an EBC 325EV ABS/DRP module.
This module provides the following vehicle performance enhancement systems.
- Antilock Brake System (ABS)
- Dynamic Rear Proportioning (DRP)
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 internal to the EBCM. The system relay is energized when the ignition is ON. The system relay supplies battery positive voltage to the valve solenoids and to the ABS 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 hydraulic pressure to each front wheel independently, and to the rear wheels as a pair.
The BPMV contains the following components.
- ABS pump motor and pump
- Three isolation valves
- Three dump valves
- A front low-pressure accumulator
- A rear low-pressure accumulator
- Wheel speed sensors (WSS) - As the wheels spin, toothed rings 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. Any imperfections in the toothed ring, such as a missing or damaged tooth, can cause an inaccurate WSS signal.