GMC 2008 Envoy Denali Owner's Manual page 117

To adjust for compass variance, do the following:
1. Find your current location and variance zone
number on the following zone map.
2. Press and hold the on/off button until a Z and a
zone number appear in the display. The compass
is now in zone mode.
3. Keep pressing the on/off button until the desired
zone number appears in the display. Release the
button. After approximately four seconds of
inactivity, the new zone number will be locked in
and the compass/temperature display will return.
4. Calibrate the compass as described next.
Compass Calibration
The compass may need calibration if one of the
following occurs:
•
After approximately five seconds, the display does
not show a compass heading (N for North, for
example), there may be a strong magnetic field
interfering with the compass. Such interference may
be caused by a magnetic antenna mount, magnetic
note pad holder or a similar magnetic item.
•
The compass does not display the correct heading
and the compass zone variance is set correctly.
In order to calibrate, CAL must be displayed in the
mirror compass windows. If CAL is not displayed, press
and hold the on/off button until CAL is displayed.
The compass can be calibrated by driving the vehicle
in circles at 5 mph (8 km/h) or less until the display
reads a direction.
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