2005 GMC Yukon Owner's Manual - Page 366

Heavy-Duty Trailer Wiring Harness Package White: Ground Light Green: Back-up Lamps Red: Battery Feed** Dark Blue: Trailer Brake **If you are charging a remote (non-vehicle) battery, turn on the headlamps to boost the vehicle system voltage and properly charge the battery. Electric Brake Control Jumper {CAUTION: Be sure to use only the correct trailer brake harness, the one intended for use on your vehicle. If you use some other trailer brake harness, even if it seems to fit, your trailer brakes may not work at all. You could have a crash in which you or others could be injured. Use only the trailer brake harness intended for your vehicle. If it is no longer available to you, be sure to get a proper replacement from your dealer. 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. The seven-wire harness contains the following trailer circuits: • Yellow: Left Stop/Turn Signal • Dark Green: Right Stop/Turn Signal • Brown: Taillamps 4-80