Knock Sensor

The first thing you must understand is diagnostic fault codes never say to replace parts or say parts are bad. They only indicate the circuit or system that needs further diagnosis. About half of the time the sensor referenced in the code is defective but half of the time there could be a corroded splice, stretched or corroded terminal in an electrical connector, or a broken or grounded wire. There are also numerous potential codes related to both of those sensors. Some describe a defective condition with the electrical circuit. Some describe an unacceptable condition that is being reported by a sensor that is working properly.

In the case of the knock sensor, if you can hear a knock in the engine, the sensor is supposed to report that. It is supposed to detect spark knock but it will respond to mechanical problems inside the engine too. In response, the Engine Computer will retard ignition timing in an attempt to stop that knock. That will result in low engine power. Replacing the knock sensor won't fix the problem it is detecting.

Can't help with the cause of the noise but anything up high is less serious than a rod knock. Often the dealer's engine specialist can tell you the cause by listening to it. Things I've run into in the past include piston slap, a cracked rocker arm, and a worn camshaft thrust plate that allows it to walk back and forth and bang on that plate.

Some engines use spring-loaded tensioners for the timing belt that also use pressurized engine oil. If that oil passage is plugged or the spring is broken they can let the timing belt slap around.

Don't overlook a loose vibration damper. That will cause a double knock each engine revolution.