need taillight wiring diagram for 91 YJ - JeepForum Jan 08, 2012Jim, there is no ground wire for the YJ tail lights. The ground is accomplished by the three mounting screws that attach the tail light housings to the body. This is why a separate ground wire must be installed for modified lights. Also, the typical aftermarket lighting wiring harnesses utilize 3 wires for STT (Stop, Tail, Turn) applications.Author: RickaysenYj Wiring DiagramsJul 31, 2017Wire Colors Please - Left Rear Tail LightApr 24, 2012tail light wiring diagramSep 17, 2011Tail light wiring harness?Jan 11, 2011See more results Jeep YJ Wiring Harness | eBay Jeep Wrangler yj engine wiring harness. all plugs and wires are in good shape removed from a running 1995 jeep wrangler with a 2.5 motor and an automatic transmission and a/c. Jeep Wrangler yj 1992-1..