2016 Silverado LT. It did not come with the backup camera, did have the tailgate lock. I purchased GM camera and new tailgate latch. Installed them myself. Took it to the dealer to get it flashed, dealer flashed the system, rear view camera showed up in setting, but no picture in reverse. Long story short, I had the camera plugged into the wrong place ( turned out where i had it plugged into was just an empty plug). I worked with the guys at the dealer, they eventually told me if the truck wasn't born with the camera, you couldn't add it. I went out to the lot and crawled under a 2016 that had a backup camera and traced the cable from the tailgate to where it plugged in. That cable had 8 wires in it, mine only had two. I surmised the backup camera and tailgate lock wiring was in the same cable. I unplugged the cable for my tailgate lock and plugged in the cable for the camera, I now had a camera but no tailgate lock. The camera plug had two empty slots, so I disassembled both plugs and moved the tailgate lock wires to the camera plug, now everything works. I have backup camera and tailgate lock. I do not have any warning sign/sounds when backing though. Not really a problem as I only really wanted it to assist in hooking up to my trailers.
Happy to help anybody with this mod.