2008 GMC Envoy Owner's Manual - Page 115

To adjust for compass variance: 1. Find your current location and variance zone number on the following zone map. 3. Scroll through the zone numbers that appear in the window on the mirror by pressing the on/off button. Once you find your zone number, release the button. After about four seconds, the mirror will return to the compass display, and the new zone number will be set. If C or CAL appears in the compass window, the compass may need calibration. See "Compass Calibration" listed previously. Automatic Dimming Rearview Mirror with OnStar®, Compass and Temperature Display Your vehicle may have this feature. When on, an automatic dimming mirror automatically dims to the proper level to minimize glare from lights behind you after dark. The mirror also includes a dual display in the upper right corner of the mirror face. The compass reading and the outside temperature will both appear in the display at the same time. 2. Press and hold the on/off button until the zone number is displayed. The number shown is the current zone number. P (On/Off): This is the on/off button. 2-41