1995 GMC Sonoma Owner's Manual - Page 114

Trailer Wiring Harness Your vehicle may have either a 5-wire or 7-wire harness. The 5-wire harness is stored under your vehicle, along the left rear frame crossmember. The harness has no connector, and you should have a qualified service person wire your harness foryou. Be sure you leave it loose enoughso the wiring doesn't bend or break, but not so loose that it drags on the ground. Store the harnessin its original place. Wrap the harness together and tie it neatly so it won't be damaged. The 7-wire is stored under your vehicle along the rear framecrossmember. This harness hasa 30 Amp. in-line fused battery feed wire and no connector, and should be wired by a qualified service person. Attach the harness to the trailer, then tape or strapit to your vehicle's frame rail. Be so sure you leave it loose enough the wiring doesn't bend or break, but not so loose that it drags on ground. the Store the harness its original place. Wrap the harness together and tie it in neatly so it won't be damaged. The fuse fortrailer wiring is in-line and located in left front side panel electrical block. 2-68