Principles of Operation

WARNING: This page is about a different car, the 2008 Mercury Sable, 2008 Ford Taurus X, and 2008 Ford Taurus. 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).

The smart junction box (SJB) monitors the door ajar switches (they are open with the door closed and closed with the door open), the hood ajar switch (closed with the hood closed and open with the hood open) and the luggage compartment lid/liftgate ajar switch (closed with the luggage compartment lid/liftgate closed). When the SJB receives a signal from one or more of the monitored switches indicating unauthorized entry into the vehicle, the SJB intermittently (in regular intervals) grounds the horn relay and also intermittently (in regular intervals) sends voltage to the turn signal lamps. The horn relay closes, supplying voltage to the horn. The SJB cycles the ground to the horn relay and voltage to the turn signal lamps, on and off, while the system is activated.