Compass Calibration and Variance Procedures
WARNING: This page is about a different car, the 2010 GMC Sierra, 2010 GMC Cab & Chassis Sierra, 2010 Chevrolet Silverado, and 2010 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
When the inside rearview mirror with compass is replaced, the compass must be setup utilizing the Compass Calibration and Magnetic Variance (without OnStar Only) .