How to Know If It’s Your Catalytic Converter Or O2 Sensor (Explained)

Are you noticing a sluggish engine performance? You are suspecting that your catalytic converter is damaged. But you know that the problem can also be with your O2 sensor. 

So, how to know if it’s your catalytic converter or O2 sensor?

Well, if any of these two are damaged, you will notice a certain performance breakdown. Such as, you might not get the acceleration that you should get. There might be continuous black smoke emitting from your exhaust pipes. Or, the exhaust smoke might give off a very pungent smell.

Worry not, as this article contains all the ways of figuring out the problem. Read the whole article to know which of your catalytic converter or O2 sensor is damaged.

Catalytic Converter Vs O2 Sensor: Basic Difference

The catalytic converter is an exhaust emission that helps to eliminate harmful toxic gases from the environment by catalyzing them in order to make the environment free from all kinds of pollution. 

It is mostly used with internal combustion engines which are fueled by gasoline or diesel. Catalytic converter plays a great role to decrease the harmful emissions from the car exhaust.

The O2 sensor is an electronic device that monitors the amount of oxygen in the exhaust gas. 

Not only does the oxygen sensor helps to control the combustion process in the engine. But it also improves the combustion efficiency of fuel and saves energy. It even helps to solve the problem of exhaust purification.

Let’s take a look at the basic differences between the catalytic converter and the O2 sensor.

Catalytic ConverterO2 sensor
It helps to reduce harmful gases It helps to measure the proportion of oxygen
It is quite expensive compared to the o2 sensor
It is cheaper than that of the catalytic converter
It reduces engine performanceIt controls the combustion process in the engine
Maintenance cost is not affordable at allThe maintenance cost of it is not as expensive as the catalytic converter
It helps to reduce harmful gases It helps to measure the proportion of oxygen

Want to know more details about it? Stay tuned, this article will show all the necessary information that’s required to know.

How Does the Oxygen Sensor Work?

Measuring Oxygen Levels

The primary function of an oxygen sensor is to measure the oxygen content in the exhaust gases. It does this by comparing the oxygen level in the exhaust with the oxygen level in the ambient air. The sensor contains a ceramic element coated with special materials that allow oxygen ions to travel through it when there is a difference in oxygen concentration between the exhaust gas and the outside air.

Generating Voltage

The oxygen sensor generates a voltage signal based on the difference in oxygen levels. When the oxygen concentration in the exhaust gas is low (indicating a rich air-fuel mixture), the sensor produces a low voltage (usually around 0.1 volts). Conversely, when the oxygen concentration is high (indicating a lean air-fuel mixture), the sensor generates a high voltage (around 0.9 volts or higher).

Sending Signals to the Engine Control Module (ECM)

The voltage signal generated by the oxygen sensor is sent to the Engine Control Module (ECM) or Engine Control Unit (ECU), which is the vehicle’s onboard computer. The ECM uses this information to adjust the air-fuel mixture in real-time. If the oxygen sensor detects a rich mixture, the ECM will reduce the amount of fuel injected into the engine. Conversely, if it detects a lean mixture, the ECM will increase the fuel injection to achieve the optimal air-fuel ratio.

Maintaining Optimal Combustion

By continuously monitoring and adjusting the air-fuel mixture, the oxygen sensor helps the engine run efficiently and reduces harmful emissions. It contributes to better fuel efficiency, lower emissions of pollutants, and overall improved engine performance.

Types of Oxygen Sensors

There are different types of oxygen sensors, including zirconia sensors and titania sensors. Zirconia sensors are the most common and operate at high temperatures, typically found in the exhaust manifold or exhaust pipe. Titania sensors, on the other hand, operate at lower temperatures and are often located downstream in the exhaust system.

How to Know If It’s Your Catalytic Converter Or O2 Sensor

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It is possible that you’re unable to guess which device is faulty. This is because both a failed oxygen sensor and a catalytic converter have the same symptoms.

At times, a faulty oxygen sensor can be a sign of your converter being bad.

Well, then how can you tell them apart? Let’s look at what we can do.

1. What If the Catalytic Converter Was Bad?

Catalytic Converters are great for reducing unwanted emissions. They even burn off the toxic pollutants that come out of your exhaust. 

If your catalytic converter is ruined, your check engine light won’t turn off. Moreover, foul sulfur-smelling exhaust gas will be emitted. This might lead to your car not running or it could keep stalling.

Other than these symptoms, you can also do a state emissions test. If the vehicle fails, it’ll determine that it was indeed your catalytic convertor.

2. Was It a Faulty O2 Sensor?

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The O2 sensor is a basic sensor wire which is the heart of modern fuel injection. These sensors impact the car’s fuel economy and catalytic converter efficiency.

The O2 sensor is used to measure the concentration of oxygen in the exhaust gas. The ECM of the sensor will decide the air mixture entered in the engine is rich or lean.

The symptoms of a bad O2 sensor and a catalytic converter are the same. The additional issue would be that the convertor would stop working first.

Checking the O2 sensor of your car is comparatively easy. You can use an Ohm meter for it. If the sensor isn’t up to mark, use an oxygen sensor socket for replacement.

If you want to buy an O2 sensor, you can get it from a nearby garage. Here are some top-picked O2 sensors for you:

Get any one of these for your car. Trust us, you won’t regret it.

If you’re still unable to tell, get a mechanic to help. Don’t prolong fixing your car otherwise, you’ll have to make a bigger investment.

Frequently Asked Questions

How long does a catalytic converter last?

A good-quality catalytic converter should last at least 10 years. Sometimes, it lasts longer, but it is better to check them in the nick of time.

How long do O2 sensors last?

Generally, an O2 sensor lasts for a runtime of about 50,000 or 60,000 miles. However, if you maintain your engine properly, the sensors might last even longer.

Will my engine be damaged if I remove the catalytic converter?

No, your engine will not be damaged just by removing the catalytic converter. Catalytic converters put a lot of strain on your engine due to their restricting effects. The engine has to work double-time to produce the energy that is needed to accelerate the car. However, time after time, your engine will gain pessimistic effects that can damage it.

What role does the O2 sensor play in the catalytic converter’s performance?

The O2 sensor measures the amount of oxygen in the exhaust gases. This data is crucial for the engine control module to adjust the air-fuel mixture. If the O2 sensor sends incorrect data to the engine control module, it can affect the catalytic converter’s efficiency, potentially leading to catalytic converter issues.

Can a failing O2 sensor trigger a check engine light similar to a faulty catalytic converter?

Yes, a failing O2 sensor can trigger a check engine light, just like a faulty catalytic converter. The O2 sensor monitors the oxygen levels in the exhaust gases, and if it malfunctions, it can provide inaccurate data to the engine control module, leading to a warning light. Proper diagnostics are essential to determine the exact cause.

What are the common signs of a failing catalytic converter, and how do they differ from O2 sensor issues?

Common signs of a failing catalytic converter include reduced acceleration, a rotten egg smell, and increased emissions. These symptoms can overlap with O2 sensor issues. However, if you notice a significant drop in fuel efficiency and power, it’s more likely related to the catalytic converter. O2 sensor issues may cause rough idling and poor engine performance.

Can a clogged catalytic converter damage the O2 sensor?

Yes, a clogged catalytic converter can lead to increased backpressure in the exhaust system, affecting the O2 sensor’s performance. Over time, this pressure can cause the O2 sensor to fail. Addressing catalytic converter issues promptly can prevent damage to the O2 sensor and other related components.


In summary, differentiating between issues with the catalytic converter and the oxygen (O2) sensor is crucial for accurate vehicle diagnostics. While both components are integral to the emission control system, specific symptoms can help discern the problem.

A failing catalytic converter often leads to reduced engine performance, overheating, or a noticeable drop in fuel efficiency. In contrast, a malfunctioning O2 sensor might cause rough idling, increased emissions, or poor fuel economy. By paying attention to these distinctive signs, car owners can pinpoint the problem accurately, allowing for timely and targeted repairs, and ultimately ensuring optimal engine performance and reduced environmental impact.

If you have come down up to this, you shouldn’t have any doubt regarding your query. Now you understand enough to tell how to know if it’s your catalytic converter or o2 sensor. 

If you face any other difficulties to resolve this problem, feel free to share with us.

Till then, best of luck.

Read also: Ball Joint Spins When Tightening Nut

Rob Dahm

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