Check engine lite code says knock sensor fault.Tell me more about this

It allows the engine to run with the 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're getting as much power and fuel economy as is possible from your engine. As long as no unusual "knocking" or "pinging" in cylinder, the sensors will go bad at some point. You may want to replace both sensors at the same point since a bit of labor to replace.