Lambda sensor: troubleshooting, purchase and replacement of the sensor on the vehicle

The lambda sensor is an important sensor in the exhaust tract of modern engines. Here, the sensor measures the residual oxygen content in the exhaust gas and makes the information available to the engine control unit. Lambda sensors are mainly used in cars with a catalytic converter. Here they ensure optimum exhaust gas values with low pollutant concentration. If the lambda sensor is defective, there are often signs such as increased fuel consumption or a drop in engine performance. Defective sensors should therefore be replaced promptly with suitable original spare parts.

Function of the lambda sensor in the car

Almost all modern vehicles have a lambda sensor located directly in the exhaust tract. There, the sensor measures the residual oxygen content in the exhaust gas and compares it with a reference, usually the ambient air. The determined value is passed on to the engine control unit in the form of an electrical signal. On the basis of these values, the engine management can recognise whether the burnt mixture is ideally adjusted, or whether it is too rich or too lean.

The measured oxygen content also has a not inconsiderable influence on exhaust gas purification. By adjusting the injection system and ignition, the engine can be operated in such a way that the exhaust gases can be optimally cleaned in the catalytic converter. Therefore, a defect in the lambda sensor can certainly lead to poor exhaust gas values. At the latest, these values can become a problem the next time the vehicle has to be presented for the general inspection.

Depending on the vehicle, two lambda sensors are possible

On most models, the lambda sensor is screwed directly into the exhaust pipe via a threaded hole and, depending on the vehicle, is located, for example,in the exhaust manifold. However, many modern vehicles have two sensors. One sensor is located in front of the catalytic converter and a second behind it. This reference sensor allows the engine to detect whether the first sensor is working optimally and to compensate for deviations accordingly.

If the lambda sensor is defective

If the lambda sensor is defective, the lambda value can no longer be clearly determined. Depending on the type of defect, the lambda sensor may provide incorrect measured values or no signal at all. As a result, the control unit for the engine can no longer access these values. Engine running can deteriorate, as can the quality of the exhaust gases.

Possible symptoms of a defective lambda sensor

Various signs can indicate a defective lambda sensor. Sometimes the engine stutters when accelerating, or the car tends to have poor throttle response in general. The engine may also run out of round or tend to consume significantly more fuel. Sometimes the exhaust gases smell unusual if the sensor is defective.

• Engine running is out of round
• Stuttering of the engine when accelerating
• Engine indicator light comes on
• Exhaust emissions are poor
• Fuel consumption is significantly increased

Since the ratio of air and fuel can no longer be optimally adjusted when the lambda sensor is defective, the concentration of pollutants in the exhaust gases increases. Some vehicles therefore switch to emergency running mode when the lambda sensor is defective. This can cause the engine control light to light up or messages in the on-board computer about an exhaust gas problem.

Other parts on the car can also be defective

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If symptoms indicate a defect in the lambda sensor, the sensor itself does not necessarily have to be defective. Sometimes the lines between the lambda sensor and engine control unit are damaged. A corroded transition at the connector can also lead to problems. Often, only a diagnosis in the workshop can provide certainty. The staff have special testing equipment and can often draw on their experience.

Replacing the lambda sensor – how to replace the component

The lambda sensor is subject to a certain amount of wear due to material ageing and heat stress, and oil in the exhaust tract can also be the cause of a defect in the sensor. Since the part cannot usually be repaired, defective lambda sensors should always be replaced with original spare parts. The exact procedure can vary depending on the model and manufacturer.

Replacing the lambda sensor from above or below

Depending on the vehicle and the position of the lambda sensor, the component can be replaced from below or from above through the engine compartment. However, it is often necessary to lift the car on a lifting platform to change the lambda sensor. After many years, the old lambda sensor is often very tight and difficult to loosen. A solid ring spanner can help here.

After the plug connection has been loosened and the defective lambda sensor removed, the intact sensor can be screwed into the exhaust system. Then reconnect the lines using the plug-in contact. Since lambda sensors differ in the number of poles and the number of lines, it is important to select the correct model when ordering spare parts.

Lambda sensor FAQ – 3 questions about the lambda sensor

1. Can lambda sensors be repaired? – If the lambda sensor in the car is defective, it usually cannot be repaired. In rare cases, cleaning the lambda sensor is useful, but most of the time the component is broken. In this case, the only solution is to replace the lambda sensor with a spare part.
2. What is a NOx sensor and what is the difference? – A NOx sensor is also a sensor within the exhaust system, similar to the lambda sensor. It is located behind the catalytic converter and measures the proportion of oxygen, but also the concentration of nitrogen oxide in the exhaust gas stream.
3. Since when have lambda sensors been installed? – The first lambda sensor was developed in the 1970s by the German manufacturer Bosch. In 1976, the series production of lambda sensors began. The first vehicle with a lambda sensor was the Volvo 240 for the US market.

Buy used lambda sensors for your car

At Autoparts24 you can find used original parts like Lambda sensors for your car. The matching car parts are listed after entering the manufacturer and vehicle model. This makes it easy to compare the prices of individual offers. In addition to the price, however, a lot of other information such as the condition is also clearly displayed. The OEM car parts are delivered directly to you after purchase by free shipping.

The advantages of buying used lambda sensors

If you want to buy spare parts such as a lambda sensor, buying used parts offers many advantages. The car parts are removed at car recyclers, and only offered in good condition. When you buy a used lambda sensor, you get reliable quality from the original manufacturer, combined with a good price. In addition, ordering used car parts protects the environment.