ok I fixed the licence plate lights and I checked the harness adapter on the truck with a voltage meter and they all seem to be working right. I think the truck may be wired different then the circuit tester and the the trailer that I connected to, but I wont know until I can find another trailer to try it on because all our other trailers have different connectors and the one I tried before no longer has any lights (its a boat trailer and im restoring the boat and trailer).
After cleaning all the dirt off and looking at the connector on truck I found that it tells what each wire is. On the side that all the truck light wires inter the connector is said something like left blinker,right blinker,parking/tail,brake,backup but no ground and on the side of the connector that you plug in to the trailer is said something like left blinker,right blinker,tail/brake,backup. That is just off the top of my head but I can check later for sure. I do know that it did not have a ground coming in or out.
03' Chevorlet 2500HD 4x4 6.0 v8
33" Dayton Timberline Mts
Tint: 20%front 5%rear
98' Ranger Sport Supercab 4x4 3.0L v6 Sold