I found these 2 plugs tucked up in the frame on the rear drivers side near the bumper mounts. They're right next to where the tail lights plug into the T connector for the 4 pin trailer harness the truck has. Anyone have an idea of what they are for?

 

Electronic brake controller is the smaller one and trailer light harness is the bigger one.

 

Where do they come out at up front?

 

Thy should be on the DS fenderwell.

 

So can these plugs be used? Wouldn't they just plug into a 7 blade trailer harness?

 

If you could find the obsolete Ford adapter they would be plug-n-play. Otherwise it is cut/solder/shrink wrap time.

 

The truck has a 4 pin pig tail installed now so I bought a 4 pin to 7 blade adapter.

 

How is the 4 pin wired? Off of your tail lights? Rip it out go get a 7 flat blade not pin and wire it up its easy and there are diagrams all over the net to follow.

 

The 4 pin adapter t's into the tail light harness. Here's something just like it on amazon:

 

When I wired in a 7 pin trailer plug on my last 4 OBS trucks I used the tail light T - adapter then cut/spliced/shrink wrapped the wires from those plugs at the back of the truck. That way I kept the 4 - wire and 7 wire capability.