Principles of Operation
WARNING: This page is about a different car, the 2010 Mercury Milan, 2010 Lincoln MKZ, and 2010 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).
Fusion
When the brake pedal is applied, voltage is routed to the SJB and the high mounted stoplamp. The SJB then supplies voltage to the rear stoplamps. The rear stoplamps are combination stop/turn lamps. The turn and hazard lamp functions override the rear stoplamp function.
Milan and MKZ
When the brake pedal is applied, voltage is routed to the high mounted stoplamp, the rear stoplamps and the SJB.