Circuit Description

The knock sensor is fitted to cylinder block to detect engine knocking. This sensor contains a piezoelectric element which generates a voltage when it becomes deformed. This occurs when cylinder block vibrates due to knocking. If engine knocking occurs, ignition timing is delayed to suppress it.

Detecting condition of DTC is when no knock sensor signal to ECM with engine speed, 2000 RPM or more. If ECM detects above diagnosis conditions, it operates fail safe function in which corrective retard angle value is set to maximum value.