Replacing the lambda sensor: Where to find the lambda sensor ?

Many motorists learn about the lambda sensor when it breaks down... Located on the exhaust line, the lambda sensor plays an essential role in the smooth running of a petrol or diesel engine. Let's find out more about the role of this sensor, which unfortunately deteriorates over the years and kilometres. We also look at the symptoms that should alert you to the need to replace a lambda sensor... Or to clean it?

What is a lambda sensor?

Before going any further, I think it's a good idea to understand the role of the lambda sensor in more detail. As its name suggests, it's a small sensor found on the exhaust line, just before the catalytic converter. Wondering what the lambda sensor does? The purpose of this sensor is to measure the oxygen content at the engine outlet. From there, the lambda sensor adapts the ratio between air and fuel. Generally speaking, you need one volume of petrol for every fourteen volumes of air - that's the ideal ratio! Otherwise, the engine runs either too rich or too lean. Either way, it's not good for your car or the environment. On some car models, a second lambda sensor is installed after the catalytic converter, to check that the information transmitted by the first has been taken into account and carried out.

The lambda sensor is therefore particularly important, as it determines how the fuel injection system works. A faulty lambda sensor can send the wrong information to the ECU, affecting the way your car works.

What causes wear to the lambda sensor?

Over time, the lambda sensor can become clogged. As a result, the information gathered may no longer be sufficiently accurate... Or even incorrect. Fortunately, there are a number of signals that can warn you if the sensor is malfunctioning. If the lambda sensor wears out, this can be due to a number of factors: clogging of the sensor, oil that can contaminate the sensor, damage to the sensor or the transmission of signals to the ECU no longer taking place. When this happens, it's a good idea to clean the lambda sensor and replace it if necessary. But before that, there's the diagnosis... How can you tell if the sensor has a problem?

How can you tell if the lambda sensor is worn?

• The engine light comes on;
• Fuel consumption increases;
• Pollution can increase drastically, which may result in a recheck at the roadworthiness test;
• Idle becomes unstable;
• Performance decreases.

Of course, these phenomena may or may not occur in combination. It all depends on the cause of the lambda sensor failure, but also on the mechanical architecture of your car. If your car has two lambda sensors, for example, the symptoms are more subtle. The whole point is to know how to test a lambda sensor. It's often during a roadworthiness test that pollution in excess of standards is detected...

How do you test a lambda sensor? Can it be cleaned?

To test a lambda sensor, you need to go through the test case. All garages and the vast majority of dealerships are able to carry out this procedure. It involves connecting an electronic suitcase to your car's OBD socket. This makes it possible to read the ECU's information and analyse any errors that may have been reported by the lambda sensor. While some mobile applications can perform this operation, the risk of error is sometimes high. So it's best to leave it to a professional.

Lambda sensor cleaning is a really good idea... But for DIY enthusiasts first! Accessing the lambda sensor can be more or less complicated, depending on the car model. Especially if the engine bay is very full! But generally speaking, it does require the removal of a few components. So having the right tools and the right knowledge is a prerequisite. But it's important to bear in mind that cleaning is an emergency solution... The sensor will certainly work again, but it will still have a few thousand kilometres behind it. Cleaning can save a few thousand kilometres, but don't expect to start again for 150,000 kilometres, which is generally the life of a lambda sensor. So it's not worth asking a garage to clean the sensor, because the labour involved in dismantling it is much higher than the value of the sensor itself. So what is the price of a lambda sensor?

How much does it cost to replace a lambda sensor?

The lambda sensor is a relatively simple, standardised part. Depending on the brand, it generally costs between €15 and €50. However, you need to add the cost of labour to this price. Depending on the car, the dismantling and reassembly stages can be more or less tedious. As a result, the cost of the operation generally fluctuates between €70 and €400. Note that some models with two sensors are less accessible...

Of course, since savings are always worthwhile, it may be tempting to put off replacing the lambda sensor. However, just like the catalytic converter, it is not advisable to drive with a faulty part. Apart from the extra fuel consumption and reduced performance, you run the risk of damaging many of your car's components. Ultimately, the risk of breakdown is greatly increased.

Image source:
Karolina Osinska / Author: ckstockphoto / Licence ID: BU98KHVSFD - elements.envato.com