With UE1
WARNING: This page is about a different car, the 2010 Cadillac DTS. However, it is still accessible from the selected car via links, so may be relevant.
The vehicle navigation radio and communication interface module (Onstar® system) both utilize the cellular microphone to receive voice commands. The cellular microphone is connected directly to the communication interface module. The navigation radio receives voice signals from the communication interface module via dedicated voice recognition circuits.