Circuit/System Description
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.
When a call is made using the mobile telephone control module, a serial data message is sent to the audio system to mute all radio functions and output the telephone call to the speakers. After the audio system is muted, the mobile telephone control module transmits signals to the audio system on the audio signal circuits.