Principles of Operation
WARNING: This page is about a different car, the 2005 Mercury Montego, 2005 Ford Freestyle, and 2005 Ford Five Hundred. However, it is still accessible from the selected car via links, so may be relevant.
The smart junction box (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 stoplamps.
If the rear stoplamps are combined with the turn lamps, the turn and hazard lamp functions override the rear stoplamp function.