unknown Error Code

My 2016 Tundra started displaying this error message at around 80-90K miles. Nothing appears to be wrong. I can still tow trailers, the brake lights all work, the brakes on the trailer are working....
I had a 100K bumper to bumper warranty so I took it to Toyota and they said they cannot figure out why it is on. At the time it was coming on randomly and then going off. There did not seem to be anything that set it off. Dealership replaced the plug at the hitch and thought maybe that was it. But the light still would come on randomly. Now, I have 106K miles. It came on a couple thousand miles ago but now is always on! Still nothing seems to be wrong with anything!!! WTF!!!!!

 

Here is a few from a post I made a long time ago. Unfortunately, I didn't find a solution. Mine went away.
https://www.tundras.com/threads/got-this-warning-today.53868/

 

Hmmm, thank you!!! how interesting! I am wondering if it has to do with my cap. I wired it myself just like I have always done with our other caps.

 

Now that you say that. My cap has been unplugged for a while and haven’t had any problems since.

But I honestly can't remember if it happened before or after I unplugged it originally.