Ifallsguy

Use a dielectric grease on you plug prior to plugging in. The grease will help keep moisture out of the truck side while not effecting power flow. A benefit is when you pull the male plug out, the dielectric leaves a film on the in truck contacts that will help protect them. Been doing that for years and haven't had an issue, even when the connection has been in water recovering a boat, snow, slush and salt of Minnesota winters and the dusty conditions of Arizona. Now I'm in southern Georgia and use it on the '16 with no problems with high humidity, heat and hurricanes.

JMENTAG

Pull fuse #35:Trailer tow stop -turn relay fuse. This will eliminate the dash alert.

In my instance on a 35K 15 MY, depressing the brake or turning on the right turn signal caused the trailer battery dash alert. I did tow a trailer using the 4 prong bumper connector the day before this alert showed up. I have not tried hooking up a trailer with this fuse pulled so further experimenting needed.

Flamingtaco

Previous response was 1.5yo...

John Voss

I have a 2018 and experienced similar behavior with my trailer. I found an RV or boating forum that this topic came up and extensive testing had been done. Many of the members over there agree that the issue is related to newer trailers with LED lights not creating enough resistance for the Truck to recognize. My trailer is a 2019 PJ and started this behavior almost immediately. I would typically get the "trailer disconnected" or "left signal fault" message. At the suggestion of the other forum, I purchased a Tow Ready 20142 7pin adapter. This adapter simulates the resistance traditional trailer lights would present to the truck. Since adding this I have 0 issues. You have to remember to unplug it when not using it else the truck thinks a trailer his attached all the time.

Flamingtaco

Use the better LED's, you won't have issues. The threshold for the current check is pretty low, but many LED's are cost leaders, using two or three LED's intended for panel mount use instead of automotive. I use Optronic Thinline for clearance and GloLight for brake/turn, they pull enough current to make the controller happy, even small trailers with only four clearance markers. A fraction of the current of halogens, but a heck of a lot brighter. LED's that have output similar to halogens (or less) are the ones that will give the truck fits.

sweilers5@gmail.com

Yes - my f150 started to do the same thing today. How did your situation turn out? Did you take it to the dealer?