Sambor

I understand that there is a member Shawnvw here on the forum that is sharp on the electronics. I have a 2011 3500HD with the nav radio but without the DVD. It came as a cab/chassis but now has a CM hauler bed. I want to install a camera in the horse trailer. My understanding is that the factory system only operates in reverse with a signal on the serial data line to the radio from the BCM. My question is this-- is there a way to fool the system to come on with either an external switch, or by just pressing the camera icon on the screen? I need to be able to just turn it on whenever I need to see the horses. Right now, my nav does not have the camera enabled, but a quick trip to the dealer will fix that. Pin 6 of radio connector X4 is camera + and pin 7 is camera-. I haven't found the serial in pin or connector yet.

Any ideas Shawnvw? Thanks for any help.

JOhn