Knock Sensor (KS): Description
A knock sensor with piezoelectric element (ceramic) is attached to the center of cylinder block of each bank #1/#2 to sense the engine knocking condition (Check for knocking for each cylinder).
The piezoelectric device output (V) = Q/C = 2dF/C (d = piezoelectric integer, C = Electrostatic capacity).
The ignition timing for MBT, Minimum spark advance for best torque, is located at the positions front and rear to the knocking limit and the ECM performs the control to make the engine to operate in optimum condition before the knocking limit.
NOTE:
When the knock sensor malfunctions, the ignition timing is corrected by the MAP values such as engine rate, air flow and engine coolant temperature, etc.