TRAILER WIRING INFORMATION - iegtoclub Trailer Wiring Information: The following diagram conforms to the standard agreed upon by vehicle manufacturers and companies producing the trailer connectors. This will allow you to hook up your old trailer to a new truck, or bring home a new commercially built trailer without any wiring hassles. Is the OEM Trailer Wiring Pattern the Same for Dodge Ford Is the OEM Trailer Wiring Pattern the Same for Dodge Ford It has been proposed to me that there is a possible difference in the wiring pattern on a seven contact trailer connection on Dodge trucks and GM trucks and Ford trucks or is the pattern the same for all trucks Factory 7-Way Wiring Color Code and Replacement Harness for 2500HD Factory Trailer Wiring Problem - GM-Trucks I have a 2003 Chevy 2500HD Crew Cab that has developed a slight electrical problem. the 12V supply lead on the factory 7 wire trailer plug doesnt supply 12 volts. I looked at the fuse block under the hood and the one on the drivers side of the dash and couldnt find any fuse that might be the culp..