Combustion Detection

Combustion Detection Signal:

Basically, the combustion detection signal is generated in the same way as the knock signal. Since a voltage is applied across the spark plugs, a weak current will flow through the spark plug where ionization (combustion) occurs.

Associated with spark plugs 1 and 2 and spark plugs 3 and 4 are sensing circuits in which the ionization current will induce a signal. This signal goes to ECM pin 17 (cylinders 1 and 2) and pin 18 (cylinders 3 and 4).

The purpose of the detection signal is to inform the ECM of the cylinder in which combustion has taken place.

Together with the positional information supplied by the crankshaft position sensor, the ECM can now determine the correct ignition timing and fuel injection sequence.