2003 GMC Sonoma Owner's Manual - Page 120

Variance is the different 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: I 1. Find your location on the zone map. Record your zone number. 2. Press and hold both the MODE and the US/MET buttons in the COMP/TEMP mode. 3. After five seconds, the compass will acknowledge the variation mode by displaying the current zone number. When it does, release both buttons. 4. Press US/MET until your zone number appears on the display. 5. Press MODE to set your zone number. Your variance is now set and the display will return to the COMPKEMP mode. 2-45