Trailer brake controller problem

I am on the Toyota portal but still looking for a wiring diagram for 2018

 

I'm adding to this thread to offer a new, different data point for this rare fault message. Hopefully it helps someone in the future.

If you have solar panels on your camper, they could be generating enough voltage to trigger the fault message.

In desperation, I unearthed this from a GM forum.



I'm getting the error message ("Trailer Warning: Type or connection fault") out of the blue, in the middle of the day. It was baffling. Turns out, my solar panels were charging throughout the day and eventually worked up enough voltage to trigger the issue.

Currently, I'm working with the dealer to devise a fix. I'll try to post a follow-up when I know more.