Trailer Wiring Diagram - Wiring Diagrams For Trailers By law, trailer lighting must be connected into the tow vehicle's wiring system to provide trailer running lights, turn signals and brake lights. This is accomplished by tapping into the tow vehicle's electrical harness to transfer power to the trailer wiring system. Trailer connectors are used between the two to allow disengagement when not WIRING DIAGRAMS Repair Guide - AutoZone AutoZone Repair Guide for your Chassis Electrical Wiring Diagrams Wiring Diagrams Related searches for gmc trailer wiring diagram gmc sierra trailer wiring diagramgmc trailer plug diagramgm trailer plug wiring diagramchevy trailer wiring harness diagramgmc truck trailer wiring diagramschevrolet truck trailer wiring diagramgmc trailer connector wire diagramgmc 7 way trailer connection