My car was throwing the SES trouble code for the knock sensor, so I replaced it and the SES light went away. I was curious, though, if anyone knows whether the SES light came on because it was a bad sensor or because it was retarding the timing? In other words, would the SES light come on if the knock sensor was detecting false or real knock...or does it only come on when it senses the KS as being faulty?

 

Real or false knock will not cause a SES light. A shorted or open sensor will throw a code.

 

The code sets when the PCM sees the incorrect voltage on the wire to the KS.... could be the wire, could be the sensor, could be a bad ground, could be a short.