Oxygen Sensor: Everything You Need to Know [O2 Sensor]

Oxygen sensor has been used in vehicles since the 1980s. O2 sensor is located in the exhaust and measures the unburnt oxygen in the burnt fuel. This measure can help the car understand between lean and rich states of the engine.

Data from the O2 sensor goes to the ECU and it accordingly adjusts the air and fuel mixture. Gasoline car engines operate at a fixed air to fuel ratio and that needs to be maintained at all times. So in this article, we will learn more about the Oxygen Sensor- what is it, how does it work and why is it important?


What is Oxygen Sensor?


The main job of an oxygen sensor is to measure the unburned oxygen content in the exhaust. It then sends this information to the ECU. If the engine has more oxygen in the fuel mixture then the engine is burning lean and if the air-fuel mixture has very little oxygen then the engine is burning rich.

Lean means the engine is getting lesser than required fuel and a rich condition means the engine is receiving extra fuel that remains unburnt during combustion.

The engine control unit will use this information to adjust the ratio of air and fuel to make sure that the engine is burning fuel properly. A faulty O2 sensor leads to lower fuel economy and poor performance.


Why is it Important?

O2 sensor is available in most of the cars manufactured after the 1980s. It is important from a performance and longevity point of view. It is also very important when it comes to the environment. O2 sensor reduces the amount of unburned gases and helps car manufacturers meet emission standards.

Newer cars may have multiple O2 sensors. After OBDII came into effect in 1996, cars were required to have an O2 sensor installed with the catalytic converter. This O2 sensor helps in monitoring the efficiency of the catalytic converter. This is important because a catalytic converter is responsible for making sure that your car is following the emission standards.


How Does Oxygen Sensor Work?


The oxygen sensor sends its readings to the ECU, which then adjusts the air-fuel mixture according to the readings. If the O2 sensor doesn’t measure the oxygen levels correctly, the ECU might not be able to adjust the air-fuel ratio and your car may perform poorly.

If the O2 level is not balanced, your car may emit a higher level of pollutants and it may lead to engine failure as well. Fuel economy, performance, and torque also drop due to a faulty O2 sensor.


Signs of Faulty O2 Sensor 

There are many ways to identify if an O2 sensor is faulty. There are some common warning signs you should look for.

  • Lower fuel economy
  • Check engine light
  • Problem when engine is idling
  • Problem when starting the engine
  • Lower torque and performance

If the check engine light comes on, you can combine it with any of the above symptoms to know for sure that the O2 sensor has failed. For additional assurance, you can use an OBD-II device to run a scan.


Oxygen Sensor Service

Sometimes oxygen sensor can get dirty and might not function properly. A dirty oxygen sensor can also trigger the check engine light on the dashboard. If you think your car is burning more fuel than usual, it is best to remove the sensor from them catalytic converter and soak it in petrol.


Locating the Oxygen Sensor 


There can be multiple O2 sensors in the car. It all depends on the year, make and model. For example, V6 and V8 engines have three O2 sensors- two on both banks and one on the catalytic converter.

The most common place to find the O2 sensor is on the back on the catalytic converter. If you are not able to locate the O2 sensor there, check the owner’s manual for the exact location.

The O2 Sensor looks like a spark plug so it is easy to identify.


Cleaning The Oxygen Sensor 

It is very easy to clean an oxygen sensor. Once you have unscrewed it from the exhaust, submerge it in petrol. For better results, keep it soaked overnight.

After leaving it overnight in petrol, take the sensor out and clean it with a towel or cotton cloth. Just reinstall it at the same location after cleaning.

You can always use an OBD-II Scanner to run a scan to see if the problem has been fixed. If you find an issue, clear the DTC  with the OBD scanner and you are good to go.

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