Been giving this some thought. Disconnect both T/signal wires at the "J" box at the pinbox. Get a good 12V test light and plug into the truck. Turn on the T/signals and see if both wires coming out of the plug harness in the "J" box light up. If they do, the problem is in the plug harness to the "J" box. Maybe some how the wire connectors have got melted together inside the plug itself. The T/signal wires run along the frame rails on each side going to the lamps themselves. Should only be 1 that controls the stop/turn on each side. There are 3 wires at the stop/turn lamps. 1 is ground,1 is tail lamp, and 1 is stop/turn. BTW, sent you a PM