Oxygen Sensor - Lifan 620 Maintenance Manual

polars of the piezoelectric crystal, and the the vibration signal will be changed into alternately
changing voltage signal and be put out. Since the frequency of the vibration signal caused by the
engine knock is much higher than that of the vibration signal caused by normal engine shock, the
ECU can tell knock signal or non-knock signal after processing the signal with wave filtering
technology. When the load, rotation speed, and coolant temperature exceed the threshold value
and no trouble information record is available for the shock sensor, the signal of the shock sensor
will be used for shock closed loop control. When the shock closed loop control is activated, the
signal of the shock sensor will be sent to the ECU for amplification and wave filtering, and then
accumulated. If the accumulation exceeds the limit within a certain crank angle, the ECU will
confirm that shock occurs and decrease the ignition advance angle at this moment. If shock still
occurs at the next cycle, the ECU will further decrease the ignition advance angle. If no shock
occurs at the following cycles, the ECU will recover the original normal ignition advance angle.
(3) Connection of wiring diagram (Fig. 1-7)
(4) Trouble diagnosis: The ECU will monitor the sensors, actuators, power amplifying circuit and
detecting circuit. In case of any of the following situations, like shock sensor trouble, shock control
data process circuit trouble, unreliable cylinder judgement signal, incorrect shock sensor trouble
mark level, and shock closed loop control closed, the ignition advance angle stored in the ECU will
be decreased for a safety angle. When the trouble frequency is lower than the set value, the
trouble mark level will be repositioned.
(5) Installation notes: The tightening torque for installation is 20±5N·m.

5. Oxygen sensor

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Fig. 1-7
(Fig. 1-8)
Fig. 1-8
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