Circuit/System Description
WARNING: This page is about a different car, the 2009 GMC Sierra and 2009 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.
The electronic brake control module (EBCM) monitors the 12 V battery positive (B+) voltage. If the voltage level is too high, damage may result in the system. When a high voltage condition is detected the EBCM turns OFF the system relay which removes 12 V battery voltage from the solenoid valves and pump motor, and DTC C0900 sets.