Hello and Welcome to Just Answer!
The Knock sensor is located above the starter near the head.
Glad to have helped. Been with Buick, Pontiac and GMC for 13 (still green!! LOL) years now. Sad to see Pontiac go, will cut our buisness down by a 1/3, and buisness sucks as it is right now anyway. But, it will turn back around soon, I hope!! Thats why I'm on here during my free time, make a little extra spending money. Take care, nice to have met you!!