2016 F-250 towing and trying to set the trailer brake gain but keep getting "no trailer connected" message on the display.

I've towed this new trailer/boat around for 10K miles or so and was able to use the manual brake previously but not now (just get the disconnected message) & as noted, can't adjust the gain.

It was originally set to 10 (factory?) when I first started towing the rig but I dialed the gain down to 6.5 readily and have had it there since because I had locked em up on a few occasions out of the gate. Recently locked em up again on a hard stop and noticed the problem when I went to adjust/lower the gain again.

I've tried it at speed on highway, around town and in the garage. Connections look good and I've tried wiggling the harness, connector ect... but it just does not seem to see the trailer is connected.

Lights all work and when I disconnect the trailer I get a trailer disconnected message as if it was seeing the trailer & recognizes when it is disconnected?

I'm guessing bad ground or connection somewhere but truck & trailer are pretty new and worked fine last 4 months.

Am I missing a setting option somewhere or do I have to chase a bad ground/connection?

BTW- I recently brought it in for a problem where my phone kept disconnecting from the bluetooth and would not take Nav update. They installed a whole new touchscreen module & I have found that I had to reset some settings (all my nav locations deleted ect...) maybe something there like a setting in the module for brakes?? I had my last trailer brake lock up after the module was replaced though so it had to be seeing the trailer at that point.

Still randomly disconnecting from my phone but seems to re-acquire the signal promptly.

Probably totally unrelated but at 70-75 the truck has a hoppy/shimmy that is super annoying. Great at 65 and gone at 80 but just doesn't want to ride smooth at 70-75. I'm open to suggestions there too!

 

I would suspect an open circuit in the trailer brake circuit. You mention 10k on the trailer, my experience with trailer brakes, at about 20k the hubs and magnets are shot and need replacing.

I would start with pulling the hubs and checking the condition of the magnets and hubs, they could have exposed windings causing the truck not to recognize a connection to the electric brakes.