I am in search of something that keeps seeming to elude me. I am trying to help a friend with a 2003 K3500 Sierra with D-max find the factory wiring schematic for the 7-prong plug. They got the truck secondhand and it had a fudged up mess there to put it short. Now, they are trying to wire it back up, but need to know what color wires do what so they can tow with the truck. Any help would be appreciated! A picture of some sort that can be printed would be the most help. Thanks in advance!