Knock Sensors (KS) - From 99MY
The ECM utilizes active knock control, which serves to prevent engine damage through pre-ignition or detonation. Knock control is effective under all operating conditions, enabling the engine to operate without additional safety margins.
Two knock sensors are used, one mounted each side of the cylinder block between the two centre cylinders of each bank. Each sensor has two wires; a signal wire providing input to the ECM and a ground (screen). Each of the sensors monitor the 'knock' from four cylinders (Cylinder No's: 1, 3, 5 & 7 and Cylinder No's: 2, 4, 6 & 8).
CAUTION: The connector and sensor terminals are gold plated to provide good conductivity and resistance to corrosion and high temperatures. Be careful not to damage terminals if probing with test equipment.
The knock sensors consist of piezo-ceramic crystals that oscillate to create a voltage signal. During pre-ignition, the frequency of crystal oscillation increases which alters the signal output to the ECM.
The signal is processed by comparing it to signal profiles contained in memory which indicate a pre-ignition condition. If pre-ignition conditions are evident, the ECM retards the ignition on that cylinder for a number of cycles. The ignition timing gradually reverts to its original setting.
The ignition system is calibrated to run on 95 RON Premium fuel for optimum fuel economy and performance characteristics. The system can also function satisfactorily with 91 RON Regular fuel. If the vehicle is refuelled with a lower grade of fuel some audible detonation may be heard until the system adoptions are complete for the new fuel grade.
If a knock sensor should fail, the following symptoms may be observed:
- Possible rough running
- Reduction in engine performance
A knock sensor failure is likely to occur for the following reasons:
- Sensor open circuit
- Short circuit to vehicle supply or ground
- Faulty component
- Loose sensor - incorrectly torqued
If knock control is disabled, a default "safe ignition map" is used.
If a knock sensor should fail, the following fault codes will be generated by the ECM diagnostics, which can be retrieved by Testbook:
- P0327 - (LH bank signal less than the threshold value determined from the ECM model above 2200 rpm)
- P0328 - (LH bank signal greater than the threshold value determined from the ECM model above 2200 rpm)
- P0332 - (RH bank signal less than the threshold value determined from the ECM model above 2200 rpm)
- P0333 - (RH bank signal greater than the threshold value determined from the ECM model above 2200 rpm)
Noise induced on the battery supply line could be misinterpreted as a knock signal and cause a maximum knock fault. A maximum fault could be caused by a short circuit to the battery supply or in the case of extreme mechanical engine noise/piston slap. A minimum fault is usually due to an open circuit.