How do you test a knock sensor to see if it is bad?
Knock sensors detect detonation ( knocking ) by reacting to the
ping by retarding the ignition timing so you will need a timing
light for this. connect the timing light and locate the knock
sensor, ( many are on the intake manifold ) now use a metal object
to tap ( not too hard and not on the sensor itself ) on the intake
manifold ( light tapping should suffice ), if the sensor is
functioning you will see the timing retard. If the timing does not
retard you will need to check voltage across the terminals of the
knock sensor connector.