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 telematics communication interface control module provides the cellular phone microphone with a supplied voltage on the cellular phone microphone high signal circuit. When the cellular phone microphone is in use, voice data from the user is sent back to the telematics communication interface control module on the microphone high signal circuit. The telematics communication interface control module provides a ground for the microphone via the microphone low signal wire.