Principles of Operation

WARNING: This page is about a different car, the 2011 Mercury Milan, 2011 Lincoln MKZ, and 2011 Ford Fusion. However, it is still accessible from the selected car via links, so may be relevant.

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

NOTE: This procedure is only applicable to vehicles without navigation. For vehicles with navigation, refer to INFORMATION & ENTERTAINMENT SYSTEMS -- FUSION, MILAN & MKZ article.

The compass display (located in the Front Display Interface Module (FDIM)) receives battery voltage from the SJB. The compass module (integral to the auto-dimming interior mirror) provides hardwired vehicle directional inputs to the Instrument Panel Cluster (IPC), which sends the compass information to the FDIM over the Medium Speed Controller Area Network (MS-CAN). 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 makes sure 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. Refer to COMPASS CALIBRATION in this service information.