unknown plug - help!
hey guys so i was wiring up a 4 wire harness to pull a trailer with. I noticed I have a plug up by where the spare wheel is mounted, it is at the far back of where the tire mounts. it is a circular plug. and it has a cap on the end of it, it is 4 wires, yellow, green, and two dark color wires with stripes. any ideas what it is for?