GM Service Manual Online
For 1990-2009 cars only

The 5A PWR MIR (FUSE 21) supplied voltage at all times to the outside rearview mirror control switch.

Both the left and right mirror assemblies contain 2 motors. One motor positions the mirror up and down. the other motor positions the mirror to the left or to the right. If you reverse the polarity of the motors, the motors move the mirrors either up and down or left and right.