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What is the difference between carb and epa catalytic converters?

When Were Catalytic Converters Required?

Diagram of a truck showing catalytic converter location

As an integral part of your vehicle’s exhaust system, the catalytic converter is designed to reduce certain gases and pollutants emitted from the exhaust of vehicles equipped with an internal combustion engine.

Since 1975, vehicles have needed a catalytic converter to meet federally mandated emission standards. For vehicle repairs, most states require an aftermarket catalytic converter that meets federal Environmental Protection Agency (EPA) standards. However, some states have enacted stricter standards that require the use of a CARB-compliant aftermarket catalytic converter to meet the standards of the California Air Resource Board (CARB).

What Makes a CARB-Compliant Catalytic Converter Different?


A catalytic converter features a substrate with a chemical coating containing precious metals like platinum, palladium and rhodium. These precious metals serve as catalysts that process regulated raw exhaust gases and convert them into the less harmful gases of water, carbon dioxide and nitrogen.

A CARB-compliant catalytic converter is one that has been approved for sale by the California Air Resources Board (CARB). CARB emission standards for aftermarket catalytic converters are more elaborate than the EPA standards for aftermarket catalytic converters and requires a more extensive warranty than the EPA.

As a result, CARB-compliant catalytic converters typically use an enhanced combination of washcoat technology and higher precious metal load to meet the stricter emissions conversions standard. A CARB-compliant converter will also have an Executive Order (EO) number/stamp on its body. The stamped number on the converter body must match the correct EO number listed on the California Air Resources Board website for aftermarket catalytic converters.

What States Use CARB-Compliant Catalytic Converters?


California became the first state to require the use of CARB-compliant catalytic converters on January 1, 2009. In recent years, Colorado (2021) and New York (2023) joined California in calling for the use of CARB-compliant catalytic converters for all model years. In addition, Maine (6/1/2018) mandated the use of CARB-compliant converters for certain model year vehicles.

STATE vehicles affected
california All model years
new york all model years
maine 2001 model years and newer vehicles
colorado all model years


Do I Need a CARB-Compliant or EPA-Compliant Catalytic Converter?

If you need a new catalytic converter, understanding if your vehicle requires a CARB-compliant converter or an EPA-compliant converter will help ensure that you get the right part. Follow these easy steps to determine which type of catalytic converter you need.

If the repair is being made in the state of California, Colorado or New York, you must use a CARB-compliant aftermarket catalytic converter for all repairs. This is true even if the vehicle was not certified as legal for sale in the state of California. Select the appropriate part as indicated in the published Walker® vehicle application data or catalog for your state.

For Maine:

Confirm the Model Year

  • In Maine, 2000 or older model years may use an EPA-compliant aftermarket catalytic converter. For these older model years, even a California-legal vehicle model may be repaired using an EPA-compliant catalytic converter. For all other model years, if the Vehicle Emission Control Information (VECI) label indicates that the vehicle has California or 50-state emission, then it must be repaired using a CARB-compliant aftermarket catalytic converter.

Find the VECI Label

  • Locate the Vehicle Emissions Control Information (VECI) label, which can be found in the engine compartment, either on the underside of the hood, on the strut tower, along the radiator support, or on the fan shroud or firewall.

Check the Label

  • Examine the label for the vehicle emissions certification to determine if the vehicle was certified as legal for sale in the state of California. The VECI label will state that the vehicle is legal for sale in the state of California or it will state that it meets emission requirements for CARB, ARB, California or 50 State emission standards. If the VECI label lists only federal or EPA emissions certification or explicitly states that the vehicle is not for sale in the state of California, the vehicle is not CARB-certified and doesn’t require the use of a CARB-compliant aftermarket converter in New York or Maine.

Note the EFN Number

  • For a CARB-certified vehicle, check the label for the engine family number (sometimes called EFN or test group number) and make a note of it. Using that number, along with the year, make and model of your vehicle, you’ll be able to find the right catalytic converter for your vehicle in the published Walker application data or catalog.

In all other states that are not mentioned above, EPA-compliant aftermarket catalytic converters may be used for all repairs regardless of whether the vehicle was certified as legal for sale in the state of California. Select the appropriate catalytic converter for your vehicle based on the recommendations in the published Walker application data or catalog.

If you have any questions, be sure to consult your state’s regulations to ensure that you get the correct converter for your application and location.

What if i use the wrong converter?

Extremely dirty truck exhaust

States that have mandated the use of CARB-compliant converters typically have emissions inspections that vehicles have to periodically pass. If you live in a state that requires the use of a CARB-compliant catalytic converter and you improperly install an EPA-compliant converter on your vehicle, you’ll likely fail your state’s emissions inspection. To pass the inspection, you’ll have to install a proper CARB-compliant catalytic converter.

For repairs in states that solely require EPA-compliant aftermarket catalytic converters, it is also allowable to install a CARB-compliant catalytic converter on your vehicle. The EPA has determined that all CARB-compliant aftermarket converters are automatically considered to be EPA-compliant. The only requirement is that the part is properly selected based on the cataloged capacities or vehicle models listed for the part in the Walker application data or catalog.

Finding an aftermarket converter

Whether you need a CARB-compliant replacement catalytic converter or an EPA-compliant converter, Walker has you covered. Walker offers premium direct fit and universal catalytic converters for both CARB and federal emissions-certified vehicles. Check out Walker’s part finder to find your catalytic converter.

Walker CalCat® catalytic converters are designed to comply with CARB requirements in California, Colorado, Maine and New York. The catalytic technology provides the proper catalyst material and design - including the right loading of precious metals and a high-technology washcoat to meet the most stringent emissions standards.

Walker Ultra® catalytic converters are engineered to meet EPA emissions requirements. Available for import and domestic OBDII (1996 and newer) vehicles, you can count on Walker catalytic converters for industry-leading fit and performance to keep the check engine light off for emissions codes.

Learn more about premium catalytic converters, find the right car part, or find a local repair shop today.

The content contained in this article is for informational purposes only and should not be used in lieu of seeking professional advice from a certified technician or mechanic. We encourage you to consult with a certified technician or mechanic if you have specific questions or concerns relating to any of the topics covered herein. Under no circumstances will we be liable for any loss or damage caused by your reliance on any content.

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