Circuit/System Description
WARNING: This page is about a different car, the 2015 Chevrolet Trax and 2015 Buick Encore. However, it is still accessible from the selected car via links, so may be relevant.
The radio provides the Cellular Phone Microphone with a supplied voltage on the Cellular Phone microphone high signal circuit. When the Microphone is in use, voice data from the user is sent back to the radio on the microphone low signal circuit.