Circuit/System Description
WARNING: This page is about a different car, the 2009 Pontiac Torrent and 2009 Chevrolet Equinox. However, it is still accessible from the selected car via links, so may be relevant.
The outside rearview mirror switch supplies both voltage and ground to the rearview mirror motors. When the rearview mirror switch is being pressed the switch supplies the voltage and ground to the proper circuits to engage the proper mirror motor.