The extra wires from the trailer connector ( orange & black , on my Freightliner chassis) were tied back to the main harness, close to the Newmar , installed fuse panel , in the center of the lower dash. Did take me about 2hrs to find.
Good luck on your search.
99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
2000 Caravan toad, Remco & Blue Ox.