Compass calibration:

First, you will need to verify that your compass zone is set to your current geographic location. Check your zone in the manual. (For example, So Cal is zone 5.)

 Here is the compass calibration adjustment procedure:

Conduct the calibration in an open area devoid of steel structures and high voltage lines. For best calibration results, be sure to turn off all electrical accessories (radio, heat, AC, wipers, etc) and make sure all doors are shut.
1. Start the Truck.
2. To enter compass calibration mode, press and display the button for eight seconds. CAL should show up in the display window.
3. Drive the vehicle slowly (3 mph or less) in circles until the CAL display indicator turns off. You may need to run 8 complete circles for calibration to be set up.
4. The compass is now calibrated.