wire diagram for trailer plug on w9

Does anyone have a link to the wiring diagram where your trailer power go through the fire wall?
The wire powering the marker lamps on the trailer died
Checked the fuses there ok
It doesn't have any power going into the tractor plug for the pig tail, took the. Plug apart and it is clean.
any pointer where to look next would be great.
I liked my old 379 the trailer wires all ran together and enter the truck in one plug.

 

Thanks for the tip grizzly!
I will check it out the next chance I get.
The hot wire is for the abs?
I had tried the relay switch,aroo
I'am inclined to think it a broken wire but the harness is in good condition so I was trying to find a known connector to test it