Circuit/System Description
WARNING: This page is about a different car, the 2013 Cadillac CTS. However, it is still accessible from the selected car via links, so may be relevant.
The radio/HVAC controls is a separate component from the radio, combined into an assembly. The assembly contains the radio control knobs and buttons for all audio and HVAC functions and the information display. The assembly is supplied battery voltage and ground . The radio uses the wake up circuit to control the power state of the display. The radio controls communicate inputs internally to the display. Display backlighting dimming level, graphical data, and radio control inputs are communicated over the CGI serial data circuits between the display and the radio.