Running/ tail light(s) coming on when truck isn't hooked up

The diagram did show up this time. Tbank you.

I guess that loose nut was completing the circuit as it was rattling around. I don't have backup lights so it doesn't matter but I do need to plug the hole to keep the water out. I didn't know what the center post was for so I didn't put it together, just brought it home. I have another class on Friday, I'll put it back together and test it then.

Thanks again for all the help.

Chris