Heated Mirrors
WARNING: This page is about a different car, the 2003 Chevrolet Corvette. However, it is still accessible from the selected car via links, so may be relevant.
The driver door module (DDM) and passenger door module (PDM) control the heated mirror functions. The DDM supplies power and ground to the driver heated mirror and the PDM supplies it to the passenger heated mirror. When the door modules receive a message on the serial data line indicating the rear defogger was turned ON, both door modules will activate the heated mirror by applying voltage to the heated mirror element feed circuit.