Chevrolet 2007 Monte Carlo Owner's Manual page 194

To adjust for compass variance, use the following
procedure:
Compass Variance Procedure
1. Press the vehicle information button until
V
PRESS TO CHANGE COMPASS ZONE
displays.
2. Find the vehicle's current location and
variance zone number on the map.
Zones 1 through 15 are available.
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3. Press the set/reset button to scroll through
and select the appropriate variance zone.
Navigate to one of the trip/fuel menu screens
to view the direction the vehicle is moving.
This will be shown in the top right corner of the
DIC display.
4. If you need to calibrate the compass, use the
compass calibration procedure. See
"Compass Calibration Procedure" following.
Compass Calibration
The compass can be manually calibrated. Only
calibrate the compass in a safe location where
driving the vehicle in circles is not a problem.
If "CAL" should ever appear in the DIC display, the
compass may need calibration.