Avh 4100-NEX unit installed in my 08 Sierra 2500HD with a Pyle backup camera for 6 years now with no issues.  I was able to acquire a 2010 tailgate with backup camera in the latch bezel which I wanted to install to my unit in place of the Pyle.  I traced out the 4 wires coming from the camera and wired as follows:  red - 12v positive, bare-12v neg/video neg, yel- video pos, and brn- trigger.  I wired the red and brown to the positive backup light.  All wires connected to the wires used for the Pyle camera.  When energizing the camera, I get video, but it continuously rolls horizontally.  After checking everything I knew to check, I gave up and hooked the pyle back up.  Now it scrolls horizontally too or doesn't come on at all.  Have I shorted something out in my head unit?