GMC 2002 Envoy - Manual (Page 124)

2-55
Compass Variance
The mirror is set to 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, such 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. Find your current location and variance zone number
on the map.
2. Press and hold the on/off button for six seconds.
Release the button when “ZONE” is displayed.
The number shown is the current zone number.
3. Scroll through the zone numbers that appear in the
compass/temperature window on the mirror by
pressing the on/off button. Once you find your zone
number, release the button. After about four seconds,
the mirror will return to the compass and
temperature display, and the new zone number will
be set.