Curious motorists have long heard of systems such as anti-lock braking system (ABS) or Stability Program (ESP), and others, too. Today we’ll talk about the Lambda probe sensor, consider the principle of operation of the Lambda probe sensor, find out why we need the Lambda probe sensor, what it is responsible for, and so on.
Every year, humanity more and more thinks about preserving the environment, because not a little has been lost in the past, we must think about the future. The legitimization of stringent environmental standards for cars has led to the development and application of new devices, such as catalytic converters.
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Catalytic converter
A catalytic converter is a device whose purpose is to reduce harmful emissions into the environment. The catalyst is a very useful thing, only for its proper operation certain conditions must be observed. The composition of the fuel-air mixture has a huge impact on the operation of the catalyst. It is on the quality of the fuel-air mixture that the life of the catalyst depends. Therefore, the Lambda probe sensor was developed, which is responsible for monitoring the composition of the same fuel-air mixture. In ordinary people it is called an oxygen sensor.
What is a lambda Sensor and what does a lambda Sensor look like?
It is no secret that the sensor got its name from the designation of the coefficient of excess air, which is indicated by the Greek letter Lambda. The lambda probe is used to measure the composition of the exhaust gases and further contributes to maintain the optimal composition of the mixture of fuel and air. The optimal ratio of the fuel-air mixture will ensure high-quality combustion, which will reduce the emission of harmful substances into the atmosphere.
The optimal composition of the fuel-air mixture is when 1 part of the fuel falls on 14.7 parts of air, while the Lambda is one. On old Soviet engines, this was difficult to achieve. And in modern cars, electronic fuel injection systems are used for this, which interacts with the Lambda probe.
How is excess air measured in a fuel-air mixture?
The excess air in the fuel-air mixture is measured by determining the content of residual oxygen (O2) in the exhaust gases. This also explains the location of the sensor in the exhaust manifold immediately in front of the catalyst.
To read the signal from the Lambda sensor, an electronic fuel injection system control unit (ECU) is used, which is responsible for optimizing the composition of the fuel-air mixture, then decreasing, then increasing the fuel supply to the engine cylinders.
Some car manufacturers went even further, and began installing two Lambda sensors in the exhaust system, before and after the catalyst. Two Lambda sensors were installed in order to increase the accuracy of preparation of the combustible mixture and improve the operation of the catalyst.
The principle of operation of the Lambda Sensor
Scheme of the oxygen sensor lambda probe based on zirconium dioxide:
1 – solid electrolyte; 2, 3 – external and internal electrodes; 4 – grounding contact; 5 – signal contact; 6 – an exhaust pipe.
The most high-quality measurement of exhaust gases by a Lambda sensor is provided at a temperature of 300-400 degrees Celsius. At this temperature, the zirconium electrolyte becomes more conductive, as a result of which the output voltage appears on the sensor electrodes.
Therefore, when starting and warming up the engine, the sensor is not used. At these engine operating modes, the air-fuel mixture quality control is performed by throttle position sensors, coolant temperature sensor, crankshaft speed sensor.
The diagram shows the dependence of the voltage of the lambda probe on the coefficient of excess air at 500-800 ° C temperature of the sensor.
For high-quality operation of the sensor at low temperatures, forced heating elements are used.
What happens if the lambda sensor does not work?
If the lambda probe sensor does not work, then the computer selects the average operating parameters, reading data from its memory. The parameters of the fuel-air mixture will vary from ideal.
What will cause a Lambda sensor failure? Damage to the Lambda sensor will lead to an increase in fuel consumption, the engine will run unevenly at idle, an increased level of CO will be contained in the exhaust gases, engine power will drop, but the car will be on the go. It’s quite difficult to check the Lambda sensor yourself, so it’s better to consult with specialists.
How long is the lambda sensor?
The life of the Lambda sensor depends on the quality of the fuel being poured. It happens that a few refueling with low-quality gasoline is enough and the sensor becomes unusable. The average life of the Lambda sensor is from 40 to 80 thousand kilometers.
