Compass: Description and Operation

COMPASS MINI-TRIP COMPUTER
The Compass Mini-Trip Computer (CMTC) is integrated into the rear view mirror. The CMTC receives CCD Bus messages which contain some of the information necessary to provide the driver with direction of vehicle travel, current outside temperature, as well as the following traveler navigational information: average fuel economy, distance to empty, instant fuel economy, elapsed time and trip odometer. This information is available in standard or metric form where applicable.

The compass is self-calibrating and usually requires no adjustment. It is located within the Electrochromic Mini-Trip Mirror (EMTM) module and is not serviced separately.

The compass will continuously perform a slow calibration to compensate for small magnetic variation common to any automobile. Uncommon magnetic shifts may be caused by items such as magnetic base antennas that can permanently alter the magnetic field of the vehicle roof panel. If an excessive magnetic field continues for five minutes, the compass heading will go blank and only the CAL symbol will illuminate. When this occurs, the vehicle roof panel may require demagnetizing. Refer to the demagnetizing procedure.

Moderate magnetic shifts may, on very rare occasions, cause the compass heading to display only one or two of the eight possible headings. Although the compass will eventually compensate for this shift, it could take several ignition cycles. The compensation process can be expedited by manually activating the fast calibration routine. Refer to the fast calibrating procedure. This procedure may be performed anytime that the compass appears to be inaccurate.

If the calibration data stored in the body control module is not received, the compass will read only NE (Northeast). The compass is self-calibrating and requires no adjusting. The word CAL is displayed to show that the compass is in calibration mode. CAL will turn off after the vehicle has gone through three complete circles without stopping in an area free of magnetic disturbance. If the module displays temperature while the compass is blank, turn OFF the ignition and run self-diagnostics. If the problem persists, demagnetize the vehicle (see the procedure for demagnetizing the vehicle).