Principles of Operation
WARNING: This page is about a different car, the 2007 Ford Ranger. However, it is still accessible from the selected car via links, so may be relevant.
Voltage is supplied at all times to the parking lamp relay. The parking lamp relay is internal to the smart junction box (SJB). Ground for the parking lamp relay coil is controlled by the headlamp switch. When the headlamp switch is placed in the PARKING LAMPS ON position, ground is supplied to the parking lamp relay. When the parking lamp relay is energized, voltage is routed from the SJB to the parking lamps.