Lambda Sensor – Working and Its Applications

The modern automobiles use various kinds of digital control systems to improve engine performance. These computerized systems rely on the inputs provided by different types of sensors present in the vehicle to control the engine, monitor emission, etc…For the good performance of the vehicle these sensors should provide accurate data or else problems such as increased fuel consumption, high emission, etc.. can occur. Some of the automobile engine sensors are the mass airflow sensors, Engine speed sensor, spark knock sensor, pressure sensor, oxygen sensor, etc… The oxygen sensor is also known as Lambda Sensor. This sensor is present at the exhaust system of the vehicle.

What is a Lambda Sensor?

Lambda Sensor, also known as an oxygen sensor, measures the amount of unburnt oxygen present in the exhaust pipe. The output of this sensor is used to adjust the air/fuel mixture in the combustion engine. This sensor helps to determine whether this air-fuel ratio is lean or rich.


The first automotive Lambda Sensor was invented by Robert Bosch GmbH in 1976. Volvo and Saab were the first to use Lambda Sensor. By the year 1993, this sensor was implemented in almost all the gasoline vehicles in Europe.

Working Principle

There are two parts in Lambda Sensor –  Sensor that gets heated and the heating sensor. The operating threshold temperature of the Lambda sensor is from 300°C to 600°C. The heating sensor helps the Lambda sensor in reaching its operating temperature.

When the engine reaches the right temperature, the sensor starts measuring the unburnt oxygen present in the exhaust gases. This output is sent to the computer unit where it calculates the air-fuel ratio and checks the look-up table to optimize this air-fuel ratio. Based on this information, a calculated amount of fuel required by the engine to burn at a stoichiometric ratio is released, ensuring complete combustion.

In automobiles two Lambda sensors are used – one installed before the catalyst converter, which controls the system and the other installed behind the catalyst converter, to make sure the former one is working properly.



The actual number of Lambda sensors present in a car depends on the year, make, model and engine of the car. Lambda sensors ( oxygen sensors)help in improving the performance of the vehicle by avoiding costly damage of CAT. Use of good Lambda sensor can cut the fuel intake of the vehicle up to 15 percentage.

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. Old sensors transmit information at very slow rates which leads to improper air/fuel mixture in catalyst converter. 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.