2004 GMC Yukon Owner's Manual - Page 374
2004 GMC Yukon Manual
Page 374 highlights
Heavy-Duty Trailer Wiring Harness Package The seven-wire harness contains the following trailer circuits: Yellow: Left Stop/Turn Signal Dark Green: Right Stop/Turn Signal Brown: Taillamps White: Ground Light Green: Back-up Lamps Red: Battery Feed Dark Blue: Trailer Brake If your trailer is equipped with electronic brakes, you can get a jumper harness (electric trailer brake control) with a trailer battery feed fuse from your dealer. This harness and fuse should be installed by your dealer or a qualified service center. Your vehicle is equipped with the seven-wire trailer towing harness. This harness with a seven-pin universal trailer connector is attached to a bracket on the hitch platform. If you need to tow a light-duty trailer with a standard four-way round pin connector, you can also get an adapter. 4-76