My 2020 Ram 2500 the last time we were towing our fifth wheel my display showed check trailer wiring, I had no trailer brakes but all lights worked. Has this happened to anyone before?

 

While its not happened to me before, I can say the very first thing I’d do is make sure that pin in your trailer socket is getting full power. Depending on this, it should give you a good indication of whether the problem is truck or trailer.

 

Do you have an added trailer socket inside the box? Not sure on the newer trucks now and what they come factory with but the add on harness for that usually plug into the backside fo the socket to add another harness and those plugs can be a poor connection. Also without that harness can be a poor connect, and also make sure your trailer cord is good condition.