Knock Sensor (KS)

KS are located on each side of engine block between cylinders No. 2 and No. 4, and between cylinders No. 3 and No. 5. KS contains a piezoelectric ceramic element which produces a voltage proportional to engine vibration. ECM uses KS signals and signals from CMP sensor and CKP sensor to verify engine knock based on positions of camshaft and crankshaft.

ECM will calculate which cylinder is knocking and retard ignition timing until knock disappears. Ignition timing will then be advanced until optimum ignition timing for suspect cylinder is achieved. For this reason it is possible for all 8 cylinders to have different ignition timing simultaneously.

If CMP sensor fails engine may run one revolution out of synchronization and ECM may retard timing of wrong cylinder in a pair. There is no default strategy for KS. If KS fails there may be increased engine noise under load conditions. A fault is indicated by illumination of the MIL.