Your 7 pin SHOULD have a ground wire that connects both the Truck and the Trailer. IF NOT, then the 5th hitch plate is the ground between the 2, which is NOT adequate. Do NOT connect the trailer to the truck. just have the hitch off the plate and then connect the 7 way and see if you get tow lights and brake lights and brake operation. You can move slightly a foot or so to see if the brakes grab. That will determine the ground situation without testing the 7 way plug. Usually the ground from the Trailer end is secured to a screw in lug in the 5th wheel hitch tongue. Doug
