Mystery 12v/30 amp plug - solved

Mystery solved Thanks everyone!!!! Can someone please tell me the purpose of this plug? The grey cap on it i says "Bosch 12v/ 20-30Amp" and except for an orange wire which seems to join the wires going to the 12v fuse box (or panel), the wires connected to the plug join all the rest of the RV wires in a large sleeve disappearing into the wall.. The plug has a cap on it and is not plugged in to anything and I don't see an outlet or connector anywhere (panel, inverter etc), and I'm guessing there's a reason the cap is on the plug, whether or not the cap belongs to that plug. I discovered this while trying to trouble shoot a non-functioning monitoring panel on a 2003 Fleetwood Tioga. Yes, I bought it used and yes, I'm a bit of a rookie! I have an inverter, a charger, and an automatic switch.

Here's a link to photos http://www.rvforum.net/SMF_forum/index.php?topic=106540.new;topicseen#new