rcompart, I posted pics of the plug in a previous reply on page 1. Take a look if you will. I chased it back as far as I can, it splits from a huge group of wires that feed into this amp looking thing in my first photos. It's not brown, it's two orange wires, one with a red stripe. I tested the ground very well, I had a bad one at first and wasn't getting a read, but after getting a solid ground, I am getting close to 8V solid.

Also, I have 2 sets of wires with 2 plugs each running to the horns. I don't think this is what this is for. Also, it has that rubber gasket like piece on the inside of the connector, like the wires that run to the ignition coil packs, presumably to keep water out of the connector.

I've pretty much ruled out most of the ideas thus far, unless it's for a fog light and all base n/a models have this wire sitting around... but I looked on the passenger side and there doesn't appear to be one there, although, it's much harder to look on that side (it's possible I could have missed one).