Hey guys, I’m new to the forum and I need your help before I go to the dealer. I have a 2016 f 350 diesel, and today when I hooked up the trailer and idled for a few minutes I get “trailer disconnected “ in the display. Fortunately the trailer was NOT disconnected! But for some reason it will not show “trailer connected”. All the lights on the trailer work fine still. The problem is the trailer brakes don’t work and every time I try to test them it just says no trailer. I tried unhooking the batteries for a bit to reset the computer but that had no effect. I don’t know what’s going on and I’m very frustrated! I hope this is a dumb little problem but I don’t know where to begin. Truck is under warranty still but I hate going to the dealer if I don’t have to. Any help is much appreciated!! Thanks in advance!

 

I've received this message before. Basically it's a failure of the connectors in the plug or receptacle. You can try cleaning it out with some plug cleaner (like an electronic plug cleaner). If that doesn't fix it, make sure your pins aren't bent so they can't make connection. Lastly, I ended up replacing one of my receptacles because it didn't have the spring-loaded door to hold the plug in snug.

 

I had the same problem with a2011. A broken wire on the trailer brakes.

 

You might as well troubleshoot it yourself and make darn sure it's not the trailer. Know anybody with a truck that you can hook the trailer to and verify it's not the trailer?

If you take it to the dealer, they'll charge a diagnostic fee, plug in a tester and tell the truck is fine.

 

I'll offer a bit of advice that has worked for me on two Ford trucks....my first one, a 2011 F250 Diesel, and my present truck, a 2016 F350 Dually. From what I have read on a couple of forums (take that for what it's worth), The plug on the trailer and the receptacle on the truck are two different brands. They are "made" to fit each other, but apparently there is a slight difference in the pin/slot configuration...in other words, when plugged in....not a tight enough fit on the connections. My solution, and it has worked on Both trucks was this. I bought a 3/4" velcro strip that was long enough to go around the plug and the little spring loaded door on the receptacle when it was plugged in. Once the trailer is plugged in, I simply make sure the door cover is pulled up tight against the plug and the "dog is in the little slot" and wrap the velcro strip around the outside of the door/plug assembly. Make sure to wrap it as tight as you can and this keeps the plug from wiggling or becoming loose. I've been doing this for about 4 or 5 years and have not ever had another trailer disconnected warning occur...on either truck, the previous one or the present on. Hope this helps.

And by the way, before I discovered this easy remedy, I had replaced the plug on the trailer $$ AND the receptacle on the truck $$$. Neither one worked, thus the velcro strap.....which has worked every single time!

 

the trailer disconnected. is only checking the trailer brake circuit...
not lights.

many problems with truck to trailer connector... weather, oxidation on the pins.
sometimes moisture in truck side connector.
clean the pins... spray... or 1000 grit sand paper....


as stated above.. try with a different truck... hook up is not needed.. just the plug.

12 dollars can get you a "Tester" for truck side.... auto parts store or Amazon.
every trailer owner should have one... my opinion.

 

Correct. The truck sends a small voltage signal down the brake control wire every 4 seconds to monitor for trailer connection. Check the pins in the connectors for the brake control wire. Then look over the trailer wiring itself. As stated above, if you have a friend that could hook their truck up to the trailer and verify the brakes work as they should that would make things easier.

As for the tester, they are great but be careful in selecting one. Some will not fool the trailer brake system and you will still get a trailer disconnected message on the dash with the tester in place. I have the tekonsha brand tester at work for testing trailer plugs and it doesn't work on the newer trucks trailer brake circuit. They all display no trailer connected.

 

Thanks everyone for your input. I think I have narrowed down where the problem must be. I hooked up my gooseneck stock trailer that uses a plug in the bed and am getting basically the same thing. This tells me the problem is in the adapter plug for the bed receptacle which basically splits the wires to go to the bumper receptacle and the bed receptacle. Since both receptacles act the same the problem must be at the split. I will unhook that and clean everything and see if that solves my problem. I'll report back and let you guys know what the results are. Thanks again for taking the time to help me!

 

Do you have the factory installed bed receptacle? If so it doesn't split between the hitch socket and in bed socket. The factory inbed plug has its own set of plugins on the left rear frame of the truck. I added the ford in bed plug in my F-250 using those capped off plugins. Still sounding like a trailer brake issue. Is the gooseneck second trailer being tried on the truck?

 

I had an issue with my hitch socket loosening from the mount. It looks fine. When it acts up I have to reach in behind it an "plug " it back into the bumper. It is on the list of things to replace when I do the bed . I mention it because it looks fine and barely moves when I do this.
After re reading you second post I see it is happening on 2 plugs. So not the same problem but just physically check all connectors looks can be deceiving. Haha