At the bottom of the "tube" for the knock sensor there is a seal to keep oil from the valley and crank case pressure from escaping. Yours might be misaligned or damaged.

 

What would cause the front knock sensor to have either oil or some type of fluid in it? I've been fighting the Low knock frequency code. So I've got a new wiring harness. I've already replaced the knock sensor once. My harness was pinched so I'm replacing it.

Thanks for the help.