I have a 2007 GMC 2500HD Diesel that has a B&W gooseneck hitch installed in the bed. At the same time I had an electrical plug installed in the bed as well. Now I get an error message on the onboard computer "service trailer brake system". I took the truck to the dealership and after many hours of troubleshooting and scratching their heads they unhooked the wiring harness for the bed plug and the problem went away. So now they (dealership) is telling me that you cannot hook an additonal plug into the stock trailer brake system wiring harness. Has anyone else had this problem? Is there a resistance or impedience issue that could be causing this problem?