Principles of Operation
WARNING: This page is about a different car, the 2009 Mercury Milan, 2009 Lincoln MKZ, and 2009 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).
The SJB monitors the input from the stoplamp switch. When the brake pedal is applied, voltage is routed to the SJB. The SJB then supplies voltage to the stoplamp.
On vehicles with combination rear stop/turn lamps, the turn and hazard lamp functions override the rear stoplamp function.