GM Service Manual Online
For 1990-2009 cars only
    • Turn the vehicle ignition switch to the ON position.
        The letter C should be displayed in the mirror compass window.
        If not, hold the COMP switch for 6 seconds until the letter C is displayed in the mirror compass window.
    • In order to check the calibration quickly, perform the following steps:
        1. Find an area free of large metal and metallic objects.
        2. Drive the vehicle in a 360 degree circle at less than 5 MPH, until the display reads a compass direction.
        3. If the compass does not calibrate after three 360° circles and the compass still displays C, replace the mirror assembly.
        4. If the compass displays C to begin with and then displays all segments after 2 minutes, refer to Magnetic Field Description .
        5. Normal calibration is achieved automatically by simply driving the vehicle.