I don't like to sound too negative, but from your posts I get a feeling that you are in way over your head.
A friend with automotive electrical experience (or a mobile RV tech) needs to "cold trace" your wiring harness.
A wrong connection usually just annoying, but it CAN be dangerous to the batteries and other electronics in both the trailer and the truck.
A degree of caution is a good idea.
A
Formerly posting as "littleblackdog"
Martha, Allen, & Blackjack
2006 Chevy 3500 D/A LB SRW, RVND 7710
Previously: 2008 Titanium 30E35SA. Currently no trailer due to age & mobility problems. Very sad!
"Real Jeeps have round headlights"