Oxygen sensor is an important part of motorcycle electronic injection system. ECU determines the low or high air-fuel ratio according to the difference of electromotive force from oxygen sensor, and controls the duration of fuel injection accordingly.

The role of the sensor is to measure the information of oxygen excess in the exhaust after combustion of the engine, namely the oxygen content, and transfer the oxygen content into voltage signal to the engine computer, so that the engine can realize the closed-loop control with excess air factor as the target.

If the oxygen sensor malfunctions and the output ELECTROmotive force is abnormal, the ECU cannot accurately control the air-fuel ratio. Therefore, the oxygen sensor can also compensate for the air-fuel ratio error caused by wear of other parts of the mechanical and electronic injection system. It can be said that the electronic injection system is the only "intelligent" sensor.

Oxygen sensors are commonly available in the first and fourth lines, as well as the second and third lines. On the first line, only one signal line is connected with the ECU, and the other pole of the sensor is directly connected with iron. Four wire, belongs to the heating type oxygen sensor, added two heating resistance wiring. The two wires, one connected to the control relay or main relay, are powered by 12V power and the other is controlled by THE ECU to control the heating time of the resistance.

The oxygen sensor works like a dc generator or a battery, producing a voltage of 0.1V to 0.9V. This voltage reflects the difference between the amount of oxygen in the exhaust gas and the amount of oxygen in the atmosphere. The greater the difference, the greater the electromotive force will be generated.

If measured with a multimeter, the ohmic resistance should be 8.1~9.5 at room temperature.

If the voltage is measured by a multimeter or an oscilloscope, the voltage will change by 0.1V~0.9V. At this time, it should be detected when the engine is running. According to the waveform, it should change more than 8 times within 10 seconds. If detected with a super test lamp, it should have a significant brightness change, which reflects a voltage change, the same as above.