Knock Control
The use of Knock Control allows the ECM to further advance the ignition timing under load for increased torque. This system uses two Knock Sensors located between cylinders 1 & 2 and between cylinders 3 & 4.
Knock Control is only in affect when the engine temperature is greater than 35° C and there is a load on the engine. This will disregard false signals while idling or from a cold engine.
Based on the firing order, the ECM monitors the Knock Sensors after each ignition for a normal (low) signal.
If the signal value exceeds the threshold, the ECM identifies the "knock" and retards the ignition timing (3°) for that cylinder the next time it is fired.
This process is repeated in 3° increments until the knock ceases. The ignition timing will be advanced again in increments right up to the knock limit and maintain the timing at that point.
If a fault is detected with the Knock Sensor(s) or circuits, the ECM deactivates Knock Control. The "CHECK ENGINE" Light will be illuminated, the ignition timing will be set to a conservative basic setting (to reduce the risk of detonation) and a fault will be stored.