Circuit/System Description
WARNING: This page is about a different car, the 2008 Cadillac CTS. However, it is still accessible from the selected car via links, so may be relevant.
When the ignition is turned ON, the radio performs a self test to verify if any critical malfunction exists within the system. Once the power-up mode is completed, the radio establishes communications with the body control module (BCM). During the power-up mode the radio checks for a valid calibration data set, if no valid calibration set is found the radio disables the system.