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 vehicle communication interface control module 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 vehicle communication interface control module on the microphone high signal circuit. The vehicle communication interface control module provides a ground for the cellular phone microphone via the low signal wire.