Circuit/System Description
WARNING: This page is about a different car, the 2012 Buick LaCrosse. However, it is still accessible from the selected car via links, so may be relevant.
The radio/HVAC controls are supplied battery voltage and ground. The radio controls the power state of the controls via a wake up circuit. Communications between the radio controls and the radio are through the CGI serial data circuits.
Communications between the HVAC controls and the HVAC control module are on a separate LIN circuit. The HVAC control module communicates status information to the radio via GMLAN for HVAC information display.