I have a honda 2013 fit sport edition, which came with the stock radio. I have replaced radio or head unit with a JVC. While I was wiring up new JVC, I can plainly see another plug that was bound tight to a cable in the back of the dash. It was unused, and bound up to be out of the way. I can clearly see a backup camera mounted under my sport rear foil, and looking at it, can see a boot and wire leading from the camera into the hatch door. This Sport was wired for a camera, but other than this mysterious plug that was bound inside the dash, I don't see anything of the other end of this wiring. What I'd love to find is some adapter plug that turns this mystery plug into an RCA jack to plug into my head unit. Please someone tell me you know what this additional plug is. When I opened my dash, I found the usual plugs for:
Radio
USB connector
Hazard light
Passenger airbag light
Antenna
Is the mystery plug not in use, for sensors for the optional navigation unit that could go in the dash? It's just a medium plug and only maybe 3 connections on it that I can see.

 

pictures would help.

 

I have a 07, BUT ,, what I noticed is that Honda seems to use the same little rectangular plugs for anything using COAX type cable, (Like the antenna connector) They sell an adapter for the antenna, you might try places like Crutchfield to see if anybody sells the BU camera adapter?