2004 Pontiac Bonneville Owner's Manual - Page 190

Secondary Information Center (SIC) Electronic Compass If your vehicle has a DIC, it also is equipped with an electronic compass. As with all compasses, this unit senses the earth's magnetic field to show the direction the vehicle is pointing. The earth's magnetic field is not always the same direction as true north as we know it. So, you must enter a zone number to tell the compass the difference between magnetic and actual north. This tells the compass where in the country you are driving. The compass remembers your zone, so you only have to change it if you drive to a new zone on the map. The compass adjusts only a small amount for each zone, so you may not notice a difference if you drive from one zone to the next one, until you cross several zones. 3-70