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What Does a Catalytic Converter Do?

If you love cars or own one, then it is important that you study about all the parts of a vehicle so you can identify and solve problems on your own.

In this article, we’ll talk about catalytic converters and what they do.

Let’s get started!

what does catalytic converter do
Catalytic converter is an important part of your car exhaust system.

What is a Catalytic Converter?

Back in school, we were taught that catalysts are compounds used to trigger a chemical reaction. They take part in a reaction but do not get affected themselves.

So, how’s a catalyst related to a vehicle? Almost all cars come with a catalytic converter. It plays a very important role in reducing emissions and keeping the environment safe.

Catalytic converters have been used for decades. In fact, the first one was developed in the 1950s by Eugene Houdry, a French engineer. These were mainly designed for use in smoke stacks but they soon got popular and by 1975 were being used in most cars.

As people became more aware of air pollution and the government started to introduce regulations to reduce pollution, manufacturers turned to catalytic converters. Today, you will find ‘em in almost all cars as they are still very effective.

What Does a Catalytic Converter Do?

Sadly, very few people understand the main purpose of a catalytic converter, which is why a lot of us do not even pay attention to it.

According to the EPA, about 60 percent of your fuel is catalyzed or burnt in the exhaust. This means a lot of your hard-earned money is going to waste. A catalytic converter can play an important role in reducing wastage, making it a good investment from a financial perspective as well.

However, the main purpose of a catalytic converter is to reduce pollution caused due to the emission of harmful gases. Hence, catalytic converters play an important role in keeping the environment safe.

Our vehicles produce harmful emissions of gases like nitrogen oxides, carbon monoxide, and hydrocarbons. These gases damage the atmosphere and can be harmful to human life as well.

The role of a catalytic converter is to reduce the amount of harmful pollutants released into the air. It takes these gases and converts them into less harmful gases and water vapors by using different chemical reactions.

According to the law, all petrol cars built in and after 1993 are required to have a catalytic converter.

How Does a Catalytic Converter Work?

Catalytic converters include a core of ceramics riddled with very small pores – smaller than 1mm.

A coat of powdered catalyst is applied over these pores. This coating is made of metals like rhodium, palladium, and platinum.

Since these pores are very close to the engine, they begin to heat up. This starts a chemical reaction and forces the chemical structure of the harmful gases to change. As a result, harmful gases get converted into oxygen and nitrogen and smog is removed.

Moreover, hydrocarbons and carbon monoxide are converted into water and carbon dioxide – less dangerous than the original gases the car produces.

A video about How To Test A Catalytic Converter

Types of Catalytic Converter

There are two types of catalytic converters, based on how effective they are:

2 Way Catalytic Converter

Also known as an oxidation catalytic converter, this one performs two tasks at once:

  • Oxidation to convert hydrocarbons into water and carbon dioxide: CxH2x+2 + [(3x+1)/2] O2 → xCO2 + (x+1) H2O
  • Oxidation to convert carbon monoxide into carbon dioxide: 2CO + O2 → 2CO2

2-way converters are more commonly used on diesel vehicles to reduce carbon monoxide and hydrocarbon emissions.

They were initially used on gasoline vehicles as well but due to their inability to reduce nitrogen oxide, which is common when it comes to gasoline vehicles, they got replaced by three-way converters in 1981.

3 Way Catalytic Converter

This type of converter became common in 1981 and has since been used in gasoline vehicles to control nitrogen oxide.

It works the same way as the 2-way converter, but is more effective as it can also work on nitrogen oxide in addition to carbon monoxide and hydrocarbons.

  • Converting nitrogen oxides into oxygen and nitrogen: 2NOx → xO2 + N2
  • Oxidation to convert hydrocarbons into water and carbon dioxide: CxH2x+2 + [(3x+1)/2] O2 → xCO2 + (x+1) H2O
  • Oxidation to convert carbon monoxide into carbon dioxide: 2CO + O2 → 2CO2

This converter works most effectively when the engine runs above the stoichiometric point.

This catalytic converter works most effectively when the engine runs above the stoichiometric point.
It works the same way as the 2-way converter, but is more effective

What is a Catalytic Converter Made Up Of?

A catalytic converter has several parts, each performing a unique function and made using specific materials:

The Substrate

The core, a ceramic monolith, typically has a honeycomb structure. Some manufacturers use Kanthal metallic foil monoliths in cases where there is extreme heat.

The Washcoat

It works as a carrier and disperses catalytic materials over a large surface area. It’s made of a variety of materials including aluminum oxide, alumina, silica, titanium dioxide, and silicon dioxide.


Manufacturers add this oxide to promote the storage of oxygen.

The Body

The main body of the catalyst is made of precious metals like platinum, rhodium, and palladium. Some manufacturers also use nickel, manganese, iron, and cerium. Moreover, legal requirements also highlight which element can be used. For example, manufacturers cannot use copper in Japan, but manufacturers in other parts of the world often use copper in the production of the body.

Since the converter contains precious metals, it is not uncommon for it to be recycled.

Where is the Catalytic Converter Located?

Since the catalytic converter is a part of the car’s exhaust system, you will find it underneath your car on the ride side of the vehicle. The exact position depends on the make and model of your vehicle.

It is usually very easy to locate due to its unique shape. Refer to the manual if you are not able to identify it.

What Happens When a Catalytic Converter Goes Bad?

It is important to be aware of the signs that indicate your vehicle’s catalytic converter is bad and needs repairs or a replacement.

Let’s look at some such signs:

Engine Misfires

Engine misfires is a common sign of a poor catalytic converter. This usually happens when the converter overheats. Moreover, an engine may also misfire due to other reasons including the presence of a rich fuel mixture in the oil tank.

This mixture can cause ignition due to raw fuel finding its way to the converter. Such situations can be very serious as the heat can cause the catalyst to begin to melt.

Poor Acceleration

Your vehicle will have a difficult time climbing hills if the catalytic converter is clogged. This is one of the most common catalytic converters-related problems. Plus, it also often gets misdiagnosed.

The easiest way to be sure is to put your vehicle through a test. If you feel the acceleration fails you then it’s time for a manual check up.

You will need a friend to help you with the test. Ask the person to hold the vehicle’s RPM between 1,800 and 2,000 only.

While the person is at it, go behind the vehicle and inspect the exhaust push with your hand. If it feels hot then there is a clog.

Reduced Performance

If you notice a sudden decrease in the engine performance then the catalytic converter might be the cause. A poor quality converter creates back pressure that can cause the engine to malfunction.

As a result, your car may shake as you drive or come to a halt all of a sudden.

Degraded Exhaust Performance

Since the role of a catalytic converter is to reduce the emission of gases, changes in the exhaust system can be a major indicator of something being wrong with the catalytic converter.

These include increased or reduced emissions, changes in the color of emissions/smoke, and changes in the pattern of how your vehicle emits gases.

If you see such signs, then make sure to make a move quick as continuing to drive your vehicle in such situations can cause the entire exhaust system to fail.

Fuel Vapor

A fuel vapor test can help you gauge the condition of your vehicle’s catalytic converter. However, it will be effective only if you have a carburetor and not a fuel infection.

The test is quite easy to perform and you will not need to turn to a professional for the job. You will, however, need the help of a friend.

Ask the friend to flash a torchlight near the carburetor and rev the engine. If you see fuel vapor over the carburetor then your vehicle’s converter has an issue.

Missing Catalytic Converter

As odd as it may sound, it is not very uncommon for thieves to steal catalytic converters. Since they contain precious metals, they can fetch a decent price when sold in scrap.

A Video about How To Diagnose A Bad Catalytic Converter 

Catalytic Converter Diagnostics:

We covered a few methods to test the catalytic converter above, but it may not be the most effective technique to diagnose a catalytic converter. This is why we suggest that you use an OBD scanner.

This is how to perform diagnosis with the help of an OBD scan tool:

  • Find a scanner that supports your make and model and offers emission tests.
  • Connect the scanner to your vehicle. Some devices are corded and some use Bluetooth technology.
  • The exact method would depend on the type of scanner you have. Nonetheless, in most cases, you will have to turn on the vehicle and leave it running for about 15 minutes so it can warm up.
  • Your scanner will give you a code which you can read to identify the problem. Some scanners will define what a code means and in some cases you will have to refer to a guide or search online for an explanation. Here are catalytic converter codes: P0420 to P0439.
  • Open live data on the scan tool and check O2 data. This is short for oxygen sensor. If the sensor fluctuates a lot then it indicates a problem.

There are a variety of scan tools out there. Most are fairly easy to use. Compare all the suitable options and pick one that suits you the best.

P.S: Some scan tools can also recommend solutions. They can help you save money by reducing trips to the mechanic. In fact, many professionals also use scan tools to identify car issues including catalytic converter issues.

Bonus: OBDLink Scan Tool: Top 4 OBD2 Scanners Review 2020

How Much is a Catalytic Converter?

Catalytic converters can be quite expensive, which is why it is important to keep ‘em well-maintained.

The average repair cost is between $945 and $2475 including labor and parts. The converter itself will cost you $2250, labor costs additional.

The Outtro

Now that you know the importance of a catalytic converter, we hope you will have no problem in maintaining it.

Read more: Check Engine Light On: What Does It Mean? Why?

Tim MillerFounderOBD Advisor

I’m Tim Miller from Denver, Colorado. I’m the founder of obdadvisor.com, an automotive blog about "Auto Diagnostic Tools and Repair Guides". My fan page is facebook.com/autozikcom. I've been working as an automotive mechanic and blogger for over 10 years writing articles to share my experiences and expertise.

Web: https://www.obdadvisor.comEmail: [email protected]
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