My 300 wiring

I've got a question for all the Mopar Mechanics. I tried to wire my 2016 Chrysler 300 with the standard 4 prong plug. It tried it with a test light and works fine. When I plug the trailer in it does strange things. Looks like it needs a special harness. Can I use the U-Haul harness that costs 50 bucks or do I have to get the harness from Chrysler which is 315.00 bucks. I know this isn't a classic car but I thought you Mopar Mechanics might be able to help me. Thanks