Chevrolet 2007 Colorado Owner's Manual page 146

Compass Calibration
The compass may need calibration if one of the
following occurs:
•
If CAL is displayed while driving in the vehicle.
•
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, push in the compass/temperature
button for approximately nine seconds or 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.
146
Compass Variance
The mirror is set in zone eight upon leaving the
factory. It will be necessary to adjust the compass
to compensate for compass variance if the
vehicle is 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.
To adjust for compass variance:
1. Find your current location and variance
zone number on the following zone map.