My truck has the tow package making the hookup as simple as plugging in the trailer connector. While using the trailer a few days ago, I have a removeable marker light on the extreme rear of the trailer where there is a lift gate attached, the light cord got stretched and broke. After repairing the broken cord the lights were checked & the running lights didn't work. There is a continuous hot battery lead at the plug and it was throwing me, because I couldn't figure why the lights wouldn't light. After 30 minutes of scratching my head I thought to check the fuse block and sure enough there is a 15amp trailer light fuse along with turns.
If you are having trailer light probs, it may save some time to check the fuses. Jeff

 

If it is like the older Dodges that fuse feeds a relay back in the wiring harnes by the rear bumper I found that the hard way.

 

My 03 has 3 seperate fuses for the trailer lighting. Running lamps, right turn, and left turn. I spent about an hour looking for a bad wire on a trailer before I finally checked the fuse box and found the bad fuse.....