OnStar Description and Operation (UI3): Microphone
WARNING: This page is about a different car, the 2018 Cadillac CTS. However, it is still accessible from the selected car via links, so may be relevant.
The microphone is located in the headliner or roof console. The telematics communication interface control module supplies approximately 10V to the microphone on the microphone signal circuit. The microphone modifies the 10V depending on the volume and voice being detected. A microphone low reference circuit or a drain wire provides a ground for the microphone. The microphone signal circuits pass through the telematics communication interface control module to support entertainment voice recognition. Thus, the module uses the same microphone as the infotainment system. In the event the infotainment system uses two microphones only one will pass through the telematics communication interface control module.