I just got a new to me 2016 Lariat 5.0 and when I hook up to my enclosed trailer I will get messages "trailer connected" followed by "trailer disconnected" it does it more often at slows speeds accelerating and braking. the lights and trailer brakes work even when it says disconnected. I will say the brakes on the trailer don't work very well but do work. Both of my last trucks would lock the wheels up and on 10 gain it barely slows the truck down. I see this is a commonly asked question but didn't see anything on 2016+ trucks. I'm going to check over my trailer to make sure everything is good but didn't have issues with my last trucks. obviously will bring this in for warranty but would like to see if you all had any input.

also I did have the dealer put in a new 7 way plug and helped a little but still comes up. So its either the programming with the truck or the trailer has some ground or brake issues from what I've read but its an all aluminum enclosed so I doubt I have a ground issue.

 

Sounds like you have an intermittent break in one (or more) of the wires.

 

I just bought a 2016 last weekend and have the same issue. The dealer found a trailer brake software update and installed it. I haven't connected to a trailer yet to find out if it fixed it.

 

Check for corrosion on the connectors, both on the truck and trailer. I had left a 4 to 7 pin connector connected to the trailer in the elements. Next time I used it the thing was giving me all kinds of fits.

 

I just connected my camper to try out the dealer update and it didnt work. They claim to have reprogrammed it per ssm45803.

 

Try putting some dielectric grease in the trailer side of the connector, plug it in and disconnect the connector a couple times then see if that helps.

My '16 truck had this issue, my camper brakes seemed a little weak, and one time when towing a family members small utility trailer I would get repeated trailer disconnected warning messages. However the utility trailer was 4 pin, and I didn't really mess with that because it wasn't mine. I found adding dielectric grease to the campers 7 pin connector helped a little, but what I did find was that I REALLY had to push the 7 pin connector in tight as I could and depending on that would effect how the brakes "felt" while towing. Made me believe it was a terminal issue personally.

I haven't had my trailer out yet with the new '18 truck, but will be towing this weekend so I'll have to see if the new truck is better.

 

Last night I decided to try towing my grandpa's 10yr old snowmobile trailer. I figure if that old thing doesn't give me an issue it has to be my camper. Sure enough after 10 miles no issues. I checked the frame ground on the camper and everything was grounded to one screw. I removed the frame paint under screw and reconnected the grounds and tried the camper again. This time I made it about a mile before the disconnect message popped up. Its better but still proves to me that there is something about my camper that is tripping the truck up.

 

Here is what the owners manual says in the information displays section.

Trailer Connected - A correct trailer connection (a trailer with electric trailer
brakes) is sensed during a given ignition cycle.

Trailer Disconnected - A trailer connection becomes disconnected, either
intentionally or unintentionally, and has been sensed
during a given ignition cycle. Disregard this status if
your vehicle is not equipped with a factory installed
trailer brake controller. This message may appear when
an aftermarket TBC is used even when the trailer is
connected.
From what I read, the trailer has to have trailer brakes for the connect message to happen.

The trailer detection system uses the trailer brake wire to sense if a trailer exists. Ground would be the other side of the circuit naturally.

 

His trailer is a heavy 4 place enclosed that has brakes. Thats why I used it as another test trailer. I didn't think about comparing resistance through the plug until I was back home. Its another thing i have on my list to check against.

 

I had the same problem with my 14 XLT and now with my 19 Lariat. I have a 16ft utility trailer and a boat, both have trailer brakes. It only occurs on the boat trailer, I never have the issue with the utility trailer.