Knock control
By analyzing the knock signal, the ECM will be able to identify the knocking cylinder and in that case how much.
If the level of knocking exceeds a specific value, ECM will retard the ignition for the cylinder in question until the knocking ceases.
The ignition timing correction will subsequently return to zero, its original setting. If the average value for the retardation on all cylinders exceeds a specific value then the mixture will be enriched.
If despite of this the average value of the timing retardation rises even more, there will be a limitation of the maximum permitted engine torque, air mass per combustion.