Circuit/System Description
WARNING: This page is about a different car, the 2011 Buick Regal. 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 signal circuit. When the microphone is in use, voice data from the user is sent back to the telematics communication interface control module on the signal circuit. The telematics communication interface control module provides a ground for the cellular phone microphone via the low reference wire.