Where is the 2009 chevy silverado knock sensor located?

The 2009 Chevy Silverado has two knock sensors on the drivers side of the engine. One slightly above and to the left of the oil filter and the other is under the third cylinder from the front. The knock sensor is basically a microphone that listens for knocks in the engine. Knocks can occur when the timing is off, bad air fuel mixture, d***y cylinders, bad spark plugs or lack of oil. The sensor sends an electrical signal to the ECU which interprets it and will adjust the ignition timing if it detects a problem. If a knock sensor fails, it can cost between $150 and $180 to have it replaced by a repair shop. You can do the job Yourself for about $20 to $30 per sensor.