sensor ? under drivers side exhaust

[junkfixr]

Can anyone tell me what the three wire thing is just under the drivers side exhause manifold ? It threads into the block and has a connector with three wires leading into the main wiring harness.

It's not the oil pressure sender, but I'm not smart enough to find it in the wiring diagrams not knowing what it's called or what purpose it serves. What the heck is it ?

 

[Mike828]

If it goes into the block it's a knock sensor.
If it goes into the oil pan it's a low oil level sensor.