Chevrolet 2002 S10 Pickup Owner's Manual page 129

Variance is the difference between magnetic north and
geographic north. In some areas, the difference between
the two can be great enough to cause false compass
readings. If this happens, follow these instructions to set
the variance for your particular location:
1. Find your location on the zone map. Record your
zone number.
2. Press and hold both the ON/OFF and the US/MET
buttons. The display will go off.
3. After five seconds, VAR CAL (Variance Calibration)
will appear on the display. When it does, release both
buttons.
4. Press US/MET until your zone number appears on
the display.
5. Press ON/OFF to enter your zone number. Your
variance is now set.
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