What Is the Catalytic Converter and What Does It Do?

Your vehicle’s exhaust system has a series of components to muffle the noise of your engine and reduce emissions. One of the most important parts for emissions reduction is a catalytic converter. Discover what is a catalytic converter, what it does, and signs that you may need your catalytic converter serviced or replaced.

What is a Catalytic Converter?

Your catalytic converter, sometimes called the cat, uses a catalyst to convert the more harmful compounds of your engine’s emissions. Typically, a combustion engine emits numerous harmful compounds. In order to protect the environment and prevent you and your family from being exposed to poisonous gases, every vehicle is required to have a catalytic converter in the emissions system.

The catalyst in your converter is typically made of palladium, rhodium, and platinum. These rare metals coat a ceramic interior, which is typically in a honeycomb or bead shape, and converts harmful gases into less harmful emissions.

Typically, your catalytic converter converts approximately 90% of emissions, but there are a number of factors that can increase or decrease the efficiency. Converters are less efficient at converting cooler temperature emissions, so a diesel fuel or short driving distances may reduce the efficiency of your converter.

A particulate filter can be added to catalytic converters to increase the efficiency to 99% by catching ultra-fine particles. Some OEM converters use a particulate filter, and many aftermarket options include this additional component.

Where is the Catalytic Converter?

Your converter is part of your exhaust system. It’s located between your headers and your muffler. The exact configuration depends on the make and model of your vehicle and the exhaust system setup. Some vehicles with dual exhaust systems use two catalytic converters, while most use a single converter for one or two exhaust pipes.

Harmful Emissions It Converts

As your internal combustion engine propels your car forward, it emits three main gases as a byproduct. Each of these gases are harmful either to your health, the environment or both. These are the three main compounds typically emitted by your engine:

  • Nitrogen oxides
  • Carbon monoxide
  • Hydrocarbons

So, what does a catalytic converter do? Your catalytic converter converts carbon monoxide into carbon dioxide, hydrocarbons into carbon dioxide, and water and nitrogen oxides into nitrogen and oxygen.

Nitrogen oxides and hydrocarbons are both causes of smog in the environment. A buildup of nitrogen oxides can create acid rain. Carbon monoxide is a poisonous gas that can be harmful or even fatal if breathed in.

What are the Signs of a Damaged Converter

Under normal operations, you can expect your converter to last up to 10 years or more. However, as it ages, a catalytic converter can become clogged, cracked or otherwise reduce its efficiency. Here are some common signs of a damaged or inefficient converter:

  • Excessive heat under your vehicle
  • Foul, sulfuric smells from your exhaust
  • Thick, dark exhaust smoke
  • Reduced engine performance and acceleration

These signs may point to a clog in your converter. Over time, the honeycomb catalyst in your converter can become clogged. This will not only reduce the efficiency of your catalyst but can completely stop exhaust gases from exiting your exhaust system. Once the catalyst is completely clogged, your engine may stall or fail to start altogether.

Another common issue is a crack in your converter or in the exhaust manifold. If there’s a crack in your exhaust system upstream of your converter, harmful gases will be emitted under your vehicle and not be properly converted. Any of these signs require immediate repair or replacement services to keep your vehicle safe.

Cleaning Your Catalytic Converter

Instead of replacing your converter, it’s possible to clean out the catalyst. Many performance issues are the result of a clogged catalyst, so follow these steps to see if you can restore the performance of your exhaust system without a costly converter replacement service:

Shop Cat Converters

How to Clean Your Catalytic Converter


Inspect Your Cat

Check to see if there are any cracks or loose parts in your converter. If not, purchase specialized catalytic converter cleaner. If there are cracks or loose parts, you'll need to repair or replace the catalytic converter.


Use the Cleaner

Follow the manufacturer's directions and tap it into your fuel tank.


Test it Out

Take a test drive to determine whether your catalyst is still clogged.

Catalytic converter cleaner won’t work if there’s any physical damage to your catalytic converter or catalyst. However, it can be used to clear off any oil or other contaminants from your catalyst and O2 sensors.

Do I Need a Catalytic Converter?

Since 1975, a catalytic converter has been required in all US vehicles. If you need to replace your catalytic converter be sure you choose a converter certified by the EPA. Operating your vehicle without a converter or with a faulty converter can be dangerous to you, everyone around you, and the environment.

Can I Upgrade My Converter?

A damaged catalytic converter needs to be replaced promptly. However, there are also some benefits of replacing your existing converter, even if it’s functioning properly. An aftermarket catalytic converter provides you with a number of performance benefits in connection with other aftermarket tune-ups.

However, don’t expect a high-flow catalytic converter to provide exceptional performance benefits alone. An aftermarket converter is a great investment if your high-performance vehicle has other aftermarket components that have increased your horsepower 20% or more above OEM levels.

While some aftermarket options may have a longer warranty, many options may not be as cost-effective as an OEM replacement. Ask a knowledgeable AutoZone associate to determine whether your car needs a new converter and whether to upgrade to an aftermarket option or stick with a reliable OEM option.

Find Out More and Shop for a New Catalytic Converter Today

Are you still unsure, “How does a catalytic converter work?” If you have more questions about this essential exhaust system component, or you need assistance in selecting the best replacement converter for your vehicle, don’t hesitate to talk with an associate at your local AutoZone, or speak with a mechanic who is knowledgeable about catalytic converter requirements, signs of a damaged converter, and the best brands to replace your damaged or clogged converter. Enjoy clean emissions, increased fuel economy, and hassle-free performance of your favorite vehicle.

Advice, how-to guides, and car care information featured on and AutoZone Advice & How-To’s are presented as helpful resources for general maintenance and automotive repairs from a general perspective only and should be used at your own risk. Information is accurate and true to the best of AutoZone’s knowledge, however, there may be omissions, errors or mistakes.

Be sure to consult your owner’s manual, a repair guide, an AutoZoner at a store near you, or a licensed, professional mechanic for vehicle-specific repair information. Refer to the service manual for specific diagnostic, repair and tool information for your particular vehicle. Always chock your wheels prior to lifting a vehicle. Always disconnect the negative battery cable before servicing an electrical application on the vehicle to protect its electrical circuits in the event that a wire is accidentally pierced or grounded. Use caution when working with automotive batteries. Sulfuric acid is caustic and can burn clothing and skin or cause blindness. Always wear gloves and safety glasses and other personal protection equipment, and work in a well-ventilated area. Should electrolyte get on your body or clothing, neutralize it immediately with a solution of baking soda and water. Do not wear ties or loose clothing when working on your vehicle.

FREE Loan-A-Tool® program requires returnable deposit. Please note that the tool that you receive after placing an online order may be in a used but operable condition due to the nature of the Loan-A-Tool® program.

Related Posts