Need location of knock sensor on 2002 Chevy Impala 3.8?

The knock sensor on a 2002 Chevy Impala 3.8L engine is located on the passenger side of the engine block, near the rear (firewall side) of the cylinder head. It's usually mounted fairly low on the block. You'll likely need to get underneath the vehicle to see it clearly.

It's a small, threaded sensor. A picture of a 3.8L engine with the sensor indicated would be highly beneficial in locating it. Searching online for "2002 Chevy Impala 3.8L engine diagram" or "2002 Chevy Impala 3.8L knock sensor location" with images should help you visualize its position.