Found Melted Switch Connector! I need help determining what its supposed to go to.

[rygar8dung]

I found a melted plug while changing my oil. it melted on the exhaust flex pipe. Its on the back of the engine block. It connects to what looks like to me a sensor just above and to the right of the oil pressure sensor. Its got two wires, red & black. I havent noticed any serious issues driving the car. I have a slight oil leak when the car is running, but that may have been caused by something else. I'm wondering if anyone knows what part this is & where its supposed to be connected to?
And if its car-life-threatening?

 

[rygar8dung]

oh ok. got it. knock sensor. where does that connect to? and my CEL is not on should i be worried?