I was replacing my spark plugs and wires and a coil pack and I noticed a little box with a connector on the passenger side of the engine bay under the the wipers. There a was what looks like a corresponding plug unplugged underneath it. Here's a pic. Sorry about the quality, my camera is screwed up.

It's a multifunction sensor. Measures humidity and ambient temps. It's for A/C

Thanks Robert. That's good to know. I imagine that plug should be plugged in then.