Radio/HVAC Communications

WARNING: This page is about a different car, the 2015 Chevrolet Camaro. However, it is still accessible from the selected car via links, so may be relevant.

Fig 1: Radio/HVAC Communications

Courtesy of GENERAL MOTORS COMPANY

Callout	Component Name
1	Radio/HVAC Controls
2	Radio
3	HVAC Control Module
4	Data link Connector
a	GMLAN
b	Local Interconnect Network-HVAC
c	CAN Graphical Interface

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.

Messages communicated between the radio and the radio/HVAC controls include the following:

Button presses/knob rotations
Info display dimming
Radio/HVAC controls back-lighting
Graphics and text information

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.