Congratulations to Joel Lake and Karen Ackerman-Mika, they correctly identified the photo of a knock sensor from a 2002 GMC Sierra. The photo was posted on our Facebook page.

A knock sensor allows the engine to run with ignition timing as far advanced as possible. The computer will continue to advance the timing until the knock sensor detects pinging. At that point the computer retards the ignition timing just enough for the pinging to stop.

A knock sensor assures that you are getting as much power and fuel economy as is possible from your engine.