2000 GMC Yukon Owner's Manual - Page 127

In order to calibrate, the letter "CAL" must be displayed in the mirror compass windows. If "CAL" is not displayed, push in the "COMP" button for approximately eight seconds or until the letter "CAL" is displayed. The compass can be calibrated in one of two ways: To adjust for compass variance: 1. Press and hold the COMP button, located at the bottom of the mirror, for three seconds until a zone number appears in the display. 2. Find your current location and variance zone number on the following zone map. D Drive the vehicle in circles at five mph (8 km/h) or less until the display reads a direction, or D Drive the vehicle on your everyday routine and after several turns the compass will become calibrated and will display a direction. Compass Variance The compass is set in zone eight upon leaving the factory. It will be necessary to adjust the compass to compensate for compass variance if you live outside zone eight. Under certain circumstances, as during a long distance cross-country trip, it will be necessary to adjust for compass variance. Compass variance is the difference between earth's magnetic north and true geographic north. If not adjusted to account for compass variance, your compass could give false readings. 3. Press the COMP button on the bottom of the mirror until the new zone number appears in the display. After you stop pressing the button in, the display will show a compass direction within a few seconds. 2-50