2003 F150 - 7700 model. I want to hook up the trailer wiring kit (from the truck to the trailer plug) but I cannot find the connector in the back of the truck. Need help. Dennis

 

on my 2001 F150, the main harness runs down the left frame rail to a plug above the axle. About 7-8 wires in the harness. At that point the rear light/ trailer harness plugs into the front harness. You can buy a new rear harness with the trailer wires in it, or just jumper the wires at the main harness to your own trailer plug. I though they all had a 4 pin connector rear harness as stock, and you have to modify if you want a 6 or 7 pin harness?

 

i had to drop the spare tire to get access to modify the plug wires.