oil leak name this part

im trying to figure out what this part is...its on an 02 civic ex it's underneath the thermostat on the engine block it looks like a small cap with a black sensor behind it.....and held on with 1 10mm bolt??????

http://i173.photobucket.com/albums/w65/mospeed1/oil.jpg (http://s173.photobucket.com/user/mospeed1/media/oil.jpg.html)

Dude.....your picture sucks. All I can see is the radiator cooling fan switch. And their ain't no oil that runs thru that passage.

Take a better one, then maybe someone might help you.