O2 Sensor (Oxygen Sensor) Importance And Functions

Majority of cars diagnosed in Nigeria for “Check Engine” light that comes on are commonly pointing out O2 sensors as one of or the only DTC (Diagnostic Trouble Codes) to be found. This O2 fault has become so common that some technicians ignore it. Ignoring this DTC is not a good idea at all because it has the potential of causing excessive fuel consumption in the car and emission failure if nothing is done. Today’s computerized engine control systems rely on inputs from a variety of sensors to regulate engine performance, emissions and other important functions. The sensors must provide accurate information otherwise drive-ability problems can result. O2 Sensor is mounted in the exhaust manifold to monitor how much unburned oxygen is in the exhaust as the burnt gases exits the vehicle through the exhaust from the engine.

How O2 sensor works

In the exhaust manifold, the oxygen sensor keeps track of the oxygen level in these exhaust gases as they leave the engine. This is oxygen that did not burn during the original air and fuel combustion. After the oxygen sensor detects the oxygen level, it sends this information back to the engine control module. The Engine Control Module (ECM) is the central computer that manages all the systems in the vehicle and communicates with a variety of different sensors that are within them.

When the Engine Control Module receives information about the oxygen level in the exhaust gases, it will know if the engine is burning too much fuel or too little fuel. For instance, if there is more air than fuel in the chamber cylinders, this will cause a lean combustion to take place. The exhaust gases that emit from such a combustion will have more oxygen in them. Once the oxygen sensor detects this and transmits the data to the engine control module, then the computer will make the proper adjustments to the timing of the fuel injectors and the operation of the engine. That way, the air and fuel mixture in the engine will be at its best for combustion purposes to maximize fuel economy.

Symptoms of bad oxygen sensor

When the oxygen sensor malfunctions it interferes with the entire internal combustion process. Then you could experience all sorts of problems with your engine while driving. Below are the top symptoms of a bad or worn out oxygen sensor. Although it is not common for this sensor to go bad, it could happen if you use bad fuel or keep your car for a long time.

Check engine light comes on: The oxygen sensor has a powerful influence over the air and fuel combustion process. If the sensor detects there to be less oxygen in the exhaust gases after combustion, the engine control module will try to correct this. But if the oxygen sensor is not working properly, the engine control module won’t know to correct this problem. As a result, the engine’s performance will be diminished. The module will then detect that some kind of engine problem is present. This causes the Check Engine warning light to illuminate on the dashboard.


Bad fuel economy: If there is a rich air and fuel mixture in any of the combustion cylinders, this means that more fuel is present than air.  This will not be detected by the oxygen sensor if it has gone bad. Then you’ll have a situation where more fuel is being burned in the engine than needed. The result is a bad fuel economy and more money spent on fuel.


Rough idling: A rough idling engine means your engine does not run steady when the car is parked or stopped. The normal RPM rate for an idle engine is under 1,000. But if your engine RPM shoots up to 2,000 or 3,000, for instance, then you have a rough idling problem. This can be a symptom of many kinds of car problems, including a bad oxygen sensor. The engine timing will be more difficult for the engine control module to manage. Then you’ll have combustion intervals which cause misfires.


Weak engine performance: Anytime there is interference in the normal combustion process of the engine, you are going to experience a weakened engine performance. This is what will happen when you have a bad oxygen sensor. You will know this is happening while you’re driving. As you step on the gas pedal, the acceleration will be limited or nonexistent.


Failed emission test: Since the oxygen sensor is located in the manifold of the exhaust system, it is able to assist with emissions control. It might not necessarily be linked to the oxygen sensor, but you will find out as soon as a mechanic checks to see why your vehicle failed the test.

Most fuel sold in Nigeria are highly leaded and commonly causes the oxygen sensor to fail. A good preventive measure is purchase fuel additives whenever you fill up your tank to help balance the chemical state of the fuel sold and improve fuel quality. You can visit our store by following this link WELCOME TO OUR STOREto order genuine fuel additives. You can also chat with us now or contact us to diagnose your car for potential oxygen sensor issue. Follow this link SCHEDULE A DIAGNOSIS APPOINTMENT to have one of our specialist check your car.

About Nonso Okafor

I've worked as a technical support representative in major auto centers in Nigeria for more than twenty years. I have dealt with a variety of problems in my capacity as a customer service representative and auto diagnostics expert. I'm committed to assisting people in properly maintaining their automobiles and in appreciating this magnificent innovation known as an automobile.

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