Lambda sensor, also known as oxygen sensor or λ-sensor, is a kind of sensor name that we can often hear. It can be seen from the name that its function is related to “oxygen content”. There are generally two oxygen sensors, one behind the exhaust pipe and the other behind the three-way catalytic converter. The former is called the front oxygen sensor, and the latter is called the rear oxygen sensor.
The oxygen sensor determines whether the fuel is burning normally by detecting the oxygen content in the schedule. Its detection results provide the ECU with important data for controlling the engine air-fuel ratio.
The role of oxygen sensor
In order to obtain a high exhaust gas purification rate and reduce the (CO) carbon monoxide, (HC) hydrocarbon and (NOx) nitrogen oxide components in the exhaust, EFI vehicles must use a three-way catalyst. But in order to be able to use the three-way catalytic converter effectively, the air-fuel ratio must be precisely controlled so that it is always close to the theoretical value. The catalytic converter is usually installed between the exhaust manifold and the muffler. The oxygen sensor has a characteristic that its output voltage has a sudden change in the vicinity of the theoretical air-fuel ratio (14.7:1). This feature is used to detect the concentration of oxygen in the exhaust and feed it back to the computer to control the air-fuel ratio. When the actual air-fuel ratio becomes higher, the concentration of oxygen in the exhaust gas increases and the oxygen sensor informs the ECU of the lean state of the mixture (small electromotive force: 0 volts). When the air-fuel ratio is lower than the theoretical air-fuel ratio, the concentration of oxygen in the exhaust gas decreases, and the status of the oxygen sensor is notified to the computer (ECU).
The ECU judges whether the air-fuel ratio is low or high based on the difference in electromotive force from the oxygen sensor, and controls the duration of fuel injection accordingly. However, if the oxygen sensor is faulty and the output electromotive force is abnormal, the (ECU) computer cannot accurately control the air-fuel ratio. Therefore, the oxygen sensor can also compensate for the error of the air-fuel ratio caused by the wear of other parts of the mechanical and electronic injection system. It can be said that it is the only “smart” sensor in the EFI system.
The function of the sensor is to determine whether the oxygen in the exhaust after combustion of the engine is excessive, that is, the oxygen content, and the oxygen content is converted into a voltage signal to the engine computer, so that the engine can realize the closed-loop control with the excess air factor as the target. The three-way catalytic converter has the greatest conversion efficiency for the three pollutants of hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxides (NOX) in the exhaust gas, and maximizes the conversion and purification of emission pollutants .
What happens if the lambda sensor fails?
The failure of the oxygen sensor and its connection line will not only cause excessive emissions, but also deteriorate the engine operating conditions, causing the vehicle to show symptoms such as idling stalls, inaccurate engine operation, and power drops. If failures occur, they must be repaired and replaced in time.
Front oxygen sensor is used to adjust the concentration of the mixed gas, and the rear oxygen sensor is to monitor the working condition of the three-way catalytic converter. The impact of the front oxygen sensor failure on the car is that the mixture cannot be corrected, which will cause the car’s fuel consumption to increase and power to drop.
Then oxygen failure means that the operating conditions of the three-way catalysis cannot be judged. Once the three-way catalysis fails, it cannot be overhauled in time, which will eventually affect the operating conditions of the engine.
Where to invest in lambda sensor?
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Post time: Nov-24-2021