Principles of Operation

Electronic Compass

Principles of Operation

NOTE: The Smart Junction Box (SJB) is also known as the Generic Electronic Module (GEM).

The compass is capable of self-calibrating. This decreases the need to manually set the compass. If the compass is displaying a heading (and not displaying the C or CAL indicator), the compass is in auto-calibration mode. In this mode, the compass automatically calibrates for changes in vehicle magnetics over the life of the vehicle. This auto-calibration mode assures the compass heading is always accurate.

If the compass displays the C or CAL indicator for an extended period of time (longer than 5 seconds), this indicates the compass has been placed in the manual calibration mode and therefore, requires manual calibration. The compass may temporarily display the C or CAL indicator if the vehicle characteristics have changed (car wash, collision or other factors), with the C or CAL indicator turning off after the vehicle characteristics have returned to normal. If the C or CAL indicator does not turn off after the vehicle characteristics have returned to normal, manual calibration will be necessary. Refer to Compass Calibration Compass Calibration. After calibration, the normal compass display will return.

Compass calibration/zone adjustment is controlled by the MODE button on the mirror, which provides access to the calibration and zone adjustment procedures. This is the same switch that is used to turn the compass display on and off.

Excessive magnetism in or near the vehicle may cause the compass to illuminate all segments on the display. In order to distinguish between vehicle magnetics and surrounding magnetics, drive the vehicle to an area that is free from large metal objects, such as bridges, steel buildings, etc. Cycling the key ON and OFF resets the compass. If all segments are still illuminated after 20 seconds, the mirror should be replaced due to excessive vehicle magnetism. Refer to Mirrors.