2005 Pontiac Aztek Owner's Manual - Page 170

Compass Variance Compass variance is the difference between magnetic north and geographic north. In some areas of the country, the difference is great enough to cause the compass to give false readings. If this occurs, the compass must be set. Compass Calibration If the calibration required symbol, or C, appears in the compass, you must manually put the compass into the calibration mode. To enter this mode, do the following: 1. Turn the ignition on and press the MODE button until CALIBRATE COMPASS displays. 2. Press and hold the SET button for longer than three seconds. ZONE - - PRESS & HOLD SET TO CHANGE: This display mode will appear when you are manually calibrating the system. When the compass is being recalibrated for the first time, the zone symbol will be displayed. When the compass is being recalibrated any time after that, the current zone number for compass variance will be displayed in place of the zone symbol. Use the SET button to select the zone number from the graphic shown to select the current area of the country that you are driving in. 3-48