GM Service Manual Online
For 1990-2009 cars only

The electronic brake control module (EBCM) performs the initialization test once each ignition cycle, when the vehicle speed reaches 15 km/h (9 mph). The initialization sequence cycles each valve solenoid and the pump motor, as well as the necessary relays, to check component operation. If any error is detected, the EBCM will set a DTC. The initialization sequence may be heard and felt while it is taking place, and is considered part of normal operation.