GMC 2002 Yukon Denali Owner's Manual page 132

Compass Calibration
The compass may need calibration if:
D
After 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.
D
The compass does not display the correct heading
and the compass zone variance is set correctly.
In order to calibrate, the letters CAL must be displayed
in the mirror compass windows. If CAL is not
displayed, push in the COMP button for approximately
eight seconds or until the letters CAL are displayed.
The compass can be calibrated in one of two ways:
D
Drive the vehicle in circles at 5 mph (8 km/h) or less
until the display reads a direction, or
D
drive the vehicle on your everyday routine and after
several turns the compass will become calibrated and
will display a direction.
2-44
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 you live 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, do the following:
1. Press and hold the COMP button located at the
bottom of the mirror for three seconds until a zone
number appears in the display.
2. Find your current location and variance zone number
on the following zone map.