ECU Detonation Control

The ECU and knock sensor are wired as shown in the diagram. When engine detonation occurs, the ECU monitors knock sensor signal feedback to determine the degree of detonation taking place. This is accomplished by filtering out sensor signal voltage which does not go above preprogrammed amplitude parameters. Because other background noise and vibration cause some signal output from the knock sensor, the ECU is also programmed to filter out any signal which does not fall within certain frequency ranges.

When the ECU judges that detonation is taking place, it retards ignition timing until the knocking stops. Timing is then advanced back to calculated value or, if detonation again begins, retarded again until detonation is stopped. In this manner, the ignition system can be operated at maximum efficiency, on the borderline of detonation, while avoiding an audible "ping." In the event that the ECU continues to sense detonation, timing retard is limited based on a clamp value stored in memory. If the ECU determines that the knock retard is not functional, it will enter a fail-safe mode and fix the retard angle to prevent engine damage.

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