I have an 08 Silverado 2500 hd with tow package. I have tried to install a tailgate light strip through the trailer harness, but it wont work. Specifically, the light strip comes with a 4 blade trailer plug. I tested it using the 7 to 4 plug adapter to make sure it would work. No go. I plug it into my son's RAM and it works. I connect a trailer to my plug and the lights on my trailer all work. Is there something strange about the trailer package that keeps this from working?