Circuit/System Description
WARNING: This page is about a different car, the 2008 Isuzu i-370, 2008 Isuzu i-290, 2008 GMC Canyon, and 2008 Chevrolet Colorado. 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.