Which sensor is this?
 

I was replacing the head gasket on my 1999 Civic Ex, and since the oils was creamy due to the head gasket failure, I had to change the oil and filter. I went ahead and took off the cylinder head. I couldn't grip the oil filter from the bottom of the car, so I tried from the top. I had to puncture through the filter to loose it. Everything was fine until I accidentally lost grip and broke the tip of that sensor. I wanted to know which sensor is that, and how do I replace it? Engine is a d16y8 Thank you.

Attachment 3904

either the knock sensor or the oil pressure sensor. I can't remember if the 99 Civic had one or not. It's been too long since I played with that type of car.

I did the same thing but with a different car and it was the Oil sending sensor I busted. Given the location I would be willing to bet it is the Oil Sensor. As easy as it is to remove that part, perhaps just pulling it and taking it to the auto parts store should reveal what it is. Knock sensor or oil pressure switch...ether way a direct comparison should do it.