GM Service Manual Online
For 1990-2009 cars only

The outside rearview mirror is electrochromic and heated. The electrochromic mirrors can be turned off and on by pressing the TEMP button the bottom of the inside rearview mirror and holding for eight seconds. A light to the right of the button will indicate if the electrochromic mirror is on or off.

To turn the defrost feature on, press the rear window defrost button. The defrost feature on the mirror will remain on the same amount of time as the rear window defroster.