Principles of Operation

The smart junction box (SJB) controls the ground circuit for the trailer tow relay coils. The SJB provides a ground to the appropriate trailer tow relay(s) to correspond with the appropriate vehicle exterior lighting requests. These requests include the parking lamps, the turn/hazard lamps and the stoplamps. When a trailer tow relay is energized, voltage is routed to the trailer tow connector. A ground circuit is also provided to the trailer tow connector.