Circuit Description
WARNING: This page is about a different car, the 2007 GMC Sierra and 2007 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.
The system relay, located within the electronic brake control module (EBCM), supplies battery voltage to all of the valve solenoids and to the Antilock Brake System (ABS) pump motor. When the relay contacts close, the EBCM monitors the voltage supplied to the valve solenoids and compares this voltage to monitored ignition voltage.