You want to know what the lambda sensor has for a task and function? Then read our blog article about this component here
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What is a lambda sensor?
In simple terms, a lambda sensor is a sensor that is installed in the exhaust tract of the vehicle to measure the residual oxygen concentration in the exhaust gas. On the basis of this value, the sensor can also ensure optimum mixture preparation/mixture composition in order to reduce or maintain the emissions of the engine.
Depending on the vehicle, up to 4 lambda sensors can be installed. A distinction is made here between pre-catalyst and post-catalyst probes.
How does a lambda sensor work?
Once the probe reaches its operating temperature of approximately 350 degrees, the residual oxygen content in the lambda probe produces a voltage change. This means in the actual sense that the functional principle is based on an oxygen comparison measurement.
The probe compares the residual oxygen in the exhaust gas (which should be approx. 0.3 – 3 %) with the oxygen content in the ambient air (approx. 20.8 – 21 %).
- If the residual oxygen content is less than about 3%, the mixture is said to be “rich” (too much fuel). Here the probe voltage rises to 0.9 V.
- If, however, the residual oxygen content is 3%, this is referred to as a “lean mixture” (too much air). Here the probe voltage is 0.1 V.
As mentioned previously, the lambda sensor measures the residual oxygen content in the exhaust gas. After the measurement, an electrical voltage is sent to the engine control unit. Based on the voltage transmitted by the probe, the engine control unit can detect whether a “rich” or “lean” mixture composition is present.
Different types of lambda sensors
There are essentially two types of lambda sensors used in a production vehicle. The so-called jump probe and the broadband probe.
Broadband probe
The great advantage of the broadband probe is that it can measure much more accurately. This is because, compared to a normal “jump probe”, the broadband probe can measure accurately even in rich and lean mixtures. Often, the broadband probe is also referred to as a “linear” probe.
Nowadays, only wideband probes are installed in new vehicles, as this type of probe meets all the criteria required for modern exhaust gas after treatment.
Jump probe
In contrast to the broadband probe, the jump probe can only send a so-called jump signal to the engine control unit. This means that the jump probe can only distinguish between rich and lean mixtures, but cannot measure exactly like the broadband probe. For this reason, the jump probe is now rarely installed in new vehicles.
What happens if the lambda sensor is defective?
If the lambda sensor is defective, the engine control lamp is usually the first to light up and the engine control unit switches to an “emergency program”. This also means that the engine control unit drastically reduces the engine power. It is also usually the case that fuel consumption increases.
Of course, the exhaust gas values of the engine also deteriorate.
Symptoms of a defect
- Illumination of the engine control lamp (MIL)
- Jerking of the engine during acceleration
- Increased fuel consumption
- Power loss
- Increased smoke from the exhaust pipe
- Failure to pass the exhaust emission test
How much does a lambda sensor cost?
The price varies depending on the model and the vehicle. As a rule, a lambda sensor costs between 50 and 200 euros. However, it is important to note that some probes for certain types of vehicles can be significantly more expensive.