small black plug.

[JDMClifford]

s13 red top sr20det

i cannot figure out whare this plug goes, its about an inch big black circle that looks like it bolts into something under the intake amnafold its hooked onto the 2 plugs onto the rear on the intake manafold, whare does it go?

[jlinder]

Knock sensor

[JDMClifford]

ok all done thank you very much