Reverse gear signal wire connection for camera

I put an AVIC-D3 in my truck last month and just purchase a Pioneer camera for it.

I run the positive from the camera power box to the ACC lead wire and the ground to the truck body.

The camera works fine when engaged through the navigation menu window but I don't have a clue on where I need to connect the wire on head unit plug labeled reverse gear signal wire.

I know that it's got to be connected somewhere so that the unitl will get the pulse that the truck is in reverse and engage the camera.

This feature is the main reason that I went with the Pioneer camera and not a cheaper one that doesn't have the reverse gear engagement.

Any help will be greatly appreciated.