Seems to me and i have not looked, shame on me, as I had my 5th wheel hitch and wiring installed for me. But I think there is a connector for the trailer wiring underneath on the drivers side door outside frame rail. Remember seeing it when I was installing running boards.
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2001 RAM 3500 dually Quad Cab SLT, 4. 10 limited slip, HO 245 hp, 6-speed, dark garnet pearl coat, interior agate, All options except heated leather, added DeeZee brite diamond tool box, Linex spray-in bed liner, Lund hood deflector 3 piece smoke color, DeeZee brite diamond cab/bed running boards and TurboSaver (from Gino's) also Reese 5th wheel 15k hitch. No plans to bomb. This is my retirment vehicle currently pulling 21' 5er want to buy 30 to 35 for retirment.