Knock Sensor: Description and Operation

Fig. 11 Knock control system.:

This system, Fig. 11, used on 1986---87 626 models, is composed of the knock sensor, EGI control unit and knock control unit. The knock sensor is installed on the engine block, where vibration occurs.
The knock control unit determines whether the signal from the knock sensor is a knocking signal or some other signal. If the signal is a knocking signal, the spark is retarded, according to the intensity of the knock, to a maximum of 6°.
The EGI control unit, in order to improve fuel consumption, sends a signal to the knock control unit in order to inhibit spark retardation at engine speeds other than 1650-4500 RPM, or when the intake manifold pressure is lower than atmospheric pressure.