Compass Calibration & Compass Magnetic Variation Adjustment: Notes
WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2003 GMC Yukon XL, 2003 GMC Yukon, 2003 Chevrolet Tahoe, 2003 Chevrolet Suburban, and 2003 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.
NOTE:
Before calibrating compass, drive vehicle to an area that is magnetically clean and free of large metallic objects such as high tension wires or steel buildings. Ensure there are no magnetized items on inside or outside of vehicle near mirror.