On my 2018 GMC 3500 SRW, Denali, the camera wire/locking tailgate plug is located between the spare tire and the factory trailer hitch. It's tight to get at without lowering the spare tire. There is a red sliding plastic locking tab which secures the plug. Slide the red locking tab away from the plug (about 3/8") with your finger nail or screwdriver but do not remove it. The tab on the plug can be depressed and the plug will separate. I plan on making or buying a short extension so that I can pull the plug through the opening in the body and unplug it without crawling under the truck. Also on my truck the support/stop cables are retained by a shoulder bolt which must be removed in order to remove the tailgate as opposed to the spring device on previous models.