What is the lambda sensor?

The lambda sensor, also called an oxygen sensor, is a small probe located on the car exhaust, between the exhaust manifold and the catalytic converter. It was developed by Volvo in the 70s.

If you own a newer car, it will be equipped with 2 lambda sensors. In that case, the second sensor will be located right behind the catalytic converter.

What is it used for?

The lambda probe will adjust the fuel amount that is sent to the engine cylinders by optimizing the air and fuel mixture, which in turn will make the engine work properly. This will also impact the harmful gas emissions rate by making sure the catalytic converter is working correctly.

Therefore, the lambda sensor ensures that your car complies with the European regulations on pollution and CO2 emissions.

How does it work?

As the lambda sensor is placed before the catalytic converter, it can measure the amount of air and fuel in the unburnt hydrocarbons after the combustion.

That way, the vehicle’s Electronic Control Unit (ECU) which controls some functionalities of the engine, will receive the correct data on the emissions, and it will then release the exact quantity of gas needed. This is essential in decreasing polluting emissions.

A faulty lambda sensor?

If the lambda sensor is defective, no data will be sent to the ECU, which will then use faulty information. This will most likely increase the fuel consumption, and subsequently, the polluting emissions.

Eventually, this may lead to the clogging of the catalytic converter, which you will then have to replace.

Symptoms of a faulty lambda sensor

• The engine warning light will show on the dashboard

• The car jerks when starting

• Unusually high fuel consumption

• Low engine power during accelerating

• A raise in emission of toxic gases

When should I replace the lambda sensor?

The lifetime of a lambda sensor is around 93,000 miles driven. However, this could be shorter depending on numerous factors that can damage it, mainly because of anomalies coming from the engine. Leaks from the exhaust can also damage the probe.

If you notice one of the signs stated above, we recommend you visit a mechanic who can test if the fault is coming from the lambda sensor. This is done with a car diagnostic tool.