How does a lambda sensor

One sensor measures the gases leaving the engine and the second sensor is located behind the catalytic converter. As the lambda sensor is a hollow ceramic cylinder, oxygen can pass through the sensor. The sensor measures the presence of oxygen and generates a voltage signal. The wires on the sensor can heat the lambda sensor and transmit the data to the ECU.

Heating the oxygen sensor also has an important reason: this allows the sensor to react quickly with a cold engine, resulting in better and more economical combustion! Now that we know this, it might be interesting for the professional to learn a short history of this part:. To tell a bit about the history of the lambda sensor, we want to take you back in time. To be precise, we have to go to for that. A little research shows that it was a very special year. And a look at the history books shows that was also a very special year for Sweden.

A real fun fact for birthdays! Well, back to the O2 sensor. As a result of stricter environmental and emission regulations that were imposed in the United States, Volvo was the first brand in who equipped this new piece of technology in the and Volvo was so proud of this innovation that it even put a genuine "Lambda Sond" emblem in the grill of several cars.

After the successful introduction, Volvo entered an even stronger partnership with Bosch, who took the responsibility of the producing the cylindrical part. The second-generation lambda sensors soon followed in The big advantage of this second generation was that this sensor was heated.

In the forty years that followed the introduction of the lambda probe, Bosch produced more than 1 billion of these parts. 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 most high-quality measurement of exhaust gases by a Lambda sensor is provided at a temperature of 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 sensor heating enables them to reach their operating temperature within a short period, keeping the time in which the lambda control is not active to a minimum.

Excessive cooling is prevented during idle mode, when the exhaust gas temperature is not as high. Heated lambda sensors have a shorter response time, which has a positive effect on the control speed. In order to receive a measurable signal for the control unit, a voltage is applied at the pump cell.

With this voltage, the oxygen can be pumped from the exhaust emissions into or out of the diffusion gap. If the mixture is lean, oxygen is pumped outward by the pump cell. A positive pump current is the result of this. If the mixture is rich, oxygen is pumped inward from the reference air. A negative pump current is the result of this. This pump current is evaluated by the control unit, providing the air ratio and thus information about the air-fuel ratio.

Since the introduction of the EOBD, the function of the catalytic converter must also be monitored. An additional lambda sensor is installed behind the catalytic converter for this.

This is used to determine the ability of the catalytic converter to store oxygen. The function of the probe downstream of the catalytic converter is the same as the upstream probe.

The amplitudes of the lambda sensors are compared in the control unit. The voltage amplitudes of the downstream probe are very small due to the ability of the catalytic converter to store oxygen. The lower the storage capacity of the catalytic converter, the higher the voltage amplitudes of the downstream probe due to the increased oxygen content.

The heights of the amplitudes at the downstream probe are dependent on the actual storage capacity of the catalytic converter, which varies depending on the load and speed. The load condition and speed are therefore taken into consideration when comparing the probe amplitudes.

If the voltage amplitudes of both probes are still roughly the same, the storage capacity of the catalytic converter has been reached, e. There are a range of typical lambda sensor faults that occur frequently. The following list shows the causes behind diagnosed faults:. Vehicles that are equipped with self-diagnostics can detect faults occurring in the control circuit and store them in the fault memory.

This is usually displayed through the engine indicator lamp. The fault memory can then be read out with a diagnostic unit for fault diagnostics. However, older systems are not able to determine whether this fault relates to a defective component or e. In this case, further tests must be carried out by the mechanic.

As part of the EOBD, the lambda sensor monitoring has been expanded to include the following points:. In order to diagnose the lambda sensor signals, the control unit uses the form of the signal frequency. Response time: Probe reacts too slowly to mixture change and no longer displays the status at the right time. If the probe voltage exceeds the control threshold, the time measurement between the positive and negative flank begins.

If the probe voltage falls short of the control threshold, the time measurement stops. The time period between the start and end of the time measurement is measured by a counter.

If the probe is severely aged or contaminated, e. The probe signal is compared with a stored signal pattern. A slow probe is detected as a fault, e. As a basic principle, a visual inspection should be carried out before each check to ensure that there is no damage to the cable or connector.

The exhaust system must not have any leaks. It is recommended to use an adapter cable to connect the measuring device. It must also be ensured that the lambda control is not active during some operating states, e. The test is carried out in the same way as the prescribed exhaust emissions test.

This sensor is highly helpful for low fuel consumption, low pollutant emission, check exhaust emission values. This sensor may get old with the passage of time and require a replacement. This leads to improper performance, increased fuel consumption by vehicle and the turning ON of engine light.

By regular descaling of the sensor and hydrogen cleaning the reliability and performance of the sensor can be improved. It is recommended to check the health of this sensor periodically. Name a specific vehicle that has 4 Lambda sensors in it.