GM Service Manual Online
For 1990-2009 cars only
  1. Turn the vehicle ignition switch to the ON position.
  2. 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.

  3. In order to check the calibration quickly, perform the following steps:
  4. 2.1. Find an area free of large metal and metallic objects.
    2.2. Drive the vehicle in a 360° circle at less than 5 MPH, until the display reads a compass direction.
    2.3. If the compass does not calibrate after three 360° circles and the compass still displays C, replace the mirror assembly.
    2.4. If the compass displays C to begin with and then displays all segments after 2 minutes, refer to Magnetic Field Description .
    2.5. Normal calibration is achieved automatically by simply driving the vehicle.