That's what the knock sensor looks like. The plug is round and looks kinda like a TPS, IACV, MAP sensor plug. Since you'll be extending it to the ECM anyway, it doesn't matter which plug you take off the JDM harness, as long as it fits onto the knock sensor. I'm sure there'll be more than one plug on the JDM harness that'll work. Just snip it off, and ad some wire to it to extend it to your ECM plug. You would need to know the pinouts for your ECM in order to know where to add the wire(s) once you've extended it to the ECM plug.