Pontiac 2005 Montana Owner's Manual page 217

Setting the Variance
Turn the ignition on and cycle the DIC to the
compass/temperature mode. Press both the E/M and
MODE buttons simultaneously for about five seconds.
The last entered variance zone number will be
displayed. Press the E/M button until the proper variance
number, as shown on the map for your location is
shown. Press the MODE button to set the new variance
zone and resume normal operation.
The display will show all the display segments briefly to
acknowledge the change in the zone number.
Automatic Compass Calibration
The compass is self-calibrating, which eliminates the
need to manually set the compass. When the vehicle is
new, the calibration process may not be complete. In
these cases the calibration symbol C will be displayed
where the compass reading is normally displayed.
To calibrate the compass, in an area free from large
metal objects, make three 360° turns. The calibration
symbol will turn off and the compass reading will
be displayed.
Manual Compass Calibration
If the compass appears erratic and the calibration
symbol does not appear, you must manually put the
compass into the calibration mode.
Turn the ignition on and cycle the DIC to the
compass/temperature mode. Press both the E/M and
MODE buttons simultaneously for at least 10 seconds
until the calibration symbol appears. Release both
buttons and complete three 360° turns in an area free
from large metal objects. The calibration symbol will turn
off and the compass reading will be displayed.
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