Principles of Operation
WARNING: This page is about a different car, the 2009 Ford Mustang. 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 rear lamps and the high mounted stoplamp.
The turn and hazard lamp functions override the rear stoplamp function.