I am probably in for the same issue if I ever use the trailer connection on my Expedition. I do know the magic way to find more stuff on this subject is to type into your search engine the, # Pin Trailer Connector, where # is the number of pins or slits in the vehicle connector. It will pull up a boat load of diagrams I reckon industry standard ones. It can also be tweaked a bit to be more specific to your vehicle once you have arrived at the pin/slit diagram page, I just was not going to sort through all of that, someday maybe, but not today, LOL. I will leave that job up to you, grin. Don't know what type of instrument set up is in your vehicle, mine is all computerized and it will tell me if the trailer is not properly connected, so the owners manual says, uh, huh, I know how that goes. That's why I got a ohms meter and kin snatch one of the neighborhood kids to help me out if I need it, its a two person job sorting that out, did it on a Dodge, not my Expedition, yet! And trust me the FORD owners manual is a vague reference as to what does what and how on your vehicle. I do know one of the pins/slits is always live, if you have power to that pin, you should be good to go from the vehicle connector as long as what you are connecting is set up the same way. One huge problem if you are dealing with the round pin type of connection, and each pin has a slit running through it's center, it's the same as a tractor trailer pigtail hook up, just smaller in scale. Those pins because of that slit can get pushed together, wiggling the connected trailer pigtail after its connected to the vehicle will cause, say the running lights to flash on and off. If that happens, take a small, I do mean small, flat blade screwdriver and gently push it into each pins slit, so it spreads the pin open/apart, be careful not to get to aggressive or you can bust one side or the other of the pin off, then its a double mint gum wrapper, seriously works like a charm on a tractor trailer pigtail! I do hate those kind of connectors, and prefer the slit type, but those pin type are cheaper so I reckon that is why they are so prolific. I will change the plug out if it is like that, and I intend to tow a trailer a lot, so far not happening with my Expedition, its an enigma anyway! If you are not getting power to that live all the time pin, then check for fuses, trust me, there is probably one in the wiring harness somewhere, then check the fuses in the vehicle fuse box. If that all checks out, you are probably better off taking it to a dealer, and just tell them to replace the wiring harness from the rear plug, tell them to reinstall a # pin slit type plug, and you can re-configure the plug on the trailer to a slit type plug, anyway from the bumper connection to where ever it connects to the vehicle the dealer needs to replace the whole harness. Or, you can pull your hair out trying to run down the short, cut wire, what ever. Course depending on your agility and age, you can do it all yourself, I'm 60+ been through 3 plane crashes and shot three times, so I aint any kind of ground monkey to try and crawl under there and figure all that out! However if you are needing to get through the fire wall or, this is a stretch, the floor of the vehicle, AMAZON has the best whatzit to do that. They sell in the aircraft section, these Molex, again, they are pin type connectors, but in this application they don't get the abuse of a trailer connection, so I have not had any issues with them. But you decide on the pin configuration, and drill a 1 to 3 inch hole in the floor or firewall, the more pins the bigger the hole, git it? These things, I will go look and find out what they are called, and get back to you. These things give you a easy through a barrier connection that is aircraft grade and water tight! Just make sure you are not going to drill into anything on the other side, and you can get to both sides to tighten the lock collar down. Takes about 10 minutes to stick one of these things in, two pin, and you have 12V DC, any where inside you need it and want to put a plug. These things are rock solid and no worries about finding the right size grommet to protect the wires on the pass through, they can handle high amperage and voltage up to 24 V+ heck they are for airplanes so they have to be safe, FAA and NTSB wont let them be used if they don't meet muster! AMAZON sells everything, my goodness, if you can think of what it may be called type that in their search bar, if it exists, they sell it. They even have a SYNC-3 system upgrade, from SYNC-2 I think, its all do it yourself, but its pretty easy, even uses the old systems connectors, so they say, plug N play. Heck these airplane things might even be a better way to run that trailer harness, keep it inside the vehicle away from weather, rocks, snags, yada, yada! Trailer electrical hook ups have always been a pain in the butt, there has to be a better way to do that people!?
