To hook up the backup camera you need to tap 3 wires on this plug. Lol, what a mess. Obviously I'm not a professional installer.
They are the red, black and white wires on the right of the plug when you are looking at it as in the picture above. The white and black wires get spliced into an RCA. The Red one goes to a 12v source.
I know the pictures are confusing so here is the wiring diagram, the plug is G20. I think your looking at the back of the stock deck in this picture so the three you want are the last three on the left in the bottom row of the G20.
Maybe your also suppose to ground it but I tried and it didn't make any difference. All I know is this worked for me. Hope this makes some sense.