GMC Sierra 2010 Owner's Manual page 281

2. Find the vehicle's current location and variance
zone number on the map.
Zones 1 through 15 are available.
3. Press the set/reset button to scroll through and
select the appropriate variance zone.
4. Press the trip/fuel button until the vehicle heading,
for example, N for North, is displayed in the DIC.
Or, if the vehicle does not have DIC buttons,
press and hold the trip odometer reset stem for
two seconds to select the next available variance
zone. Repeat this step until the appropriate
variance zone is displayed.
5. If calibration is necessary, calibrate the compass.
See Compass Calibration Procedure following.
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