Knock Sensor

Vibrations in engine block will cause the quartz crystal inside knock sensor to produce a small voltage. The ECU monitors this small voltage. Ignition timing is retarded 3 degrees initially when detonation begins to occur. Timing is retarded only in the cylinder which is detonating.

When detonation stops, ignition timing is advanced in .33 degree increments until a preprogrammed value is reached. If detonation continues or reoccurs in a cylinder, ignition timing can be retarded up to 15 degrees for each cylinder. The difference between any 2 cylinders is limited to 9 degrees.