By Pablora Parts LLC parts specialists · Updated September 8, 2026 · Part of Catalytic converters
Aftermarket catalytic converters come in two legal categories, and buying the wrong one is an expensive mistake: the converter is fine, the truck runs fine, and the vehicle still fails inspection because the paperwork does not match the state. This guide explains the two categories, which states use which, and what to have ready when you order.
Federal (EPA) converters
A federal converter meets the EPA's aftermarket converter standard and is legal to install in the 46 states that follow federal rules, often sold as 49-state converters. They are cheaper, carry a shorter warranty, and are what most online listings show by default. Under EPA rules an aftermarket converter may only be installed when the original is missing, has failed a test, or the vehicle is past its emissions warranty, and the installer is supposed to keep a record.
CARB-certified converters
California's Air Resources Board runs a stricter program. A CARB-certified converter has passed durability and emissions testing for specific engine families and carries an Executive Order number, formatted like D-193-135, that is stamped on the converter and listed in CARB's database against the exact vehicles it is approved for. CARB converters use more precious metal, cost more, and carry a longer warranty on the substrate.
A CARB converter is legal everywhere. A federal converter is not legal in a CARB state, and inspection stations in those states check for the EO stamp.
Which states require CARB
California, obviously. New York adopted California's aftermarket converter rules in 2013, Maine in 2018 and Colorado from 2021 for the vehicles its rule covers. Other states have considered it. If the vehicle is registered in any of these, or you plan to move there, buy the CARB unit. If you are in Texas, Florida or the Midwest, a federal converter is legal and fine.
What matters is the state of registration, not where the truck was built or bought. A truck bought in Nevada and registered in California needs a CARB converter.
Matching the converter to the engine
CARB approval is per engine family and model year, so the same converter listing will show as legal for some years of a Traverse 3.6 and not others. V6 and V8 engines have one converter per bank, and the bank 1 and bank 2 parts are different. A P0420 code points to bank 1, P0430 to bank 2. The underhood emissions label states the certification the vehicle was built to, which decides the converter family even outside California.
Direct-fit converters bolt into place. Universal converters need cutting and welding and are not CARB-approved for most late-model vehicles, so a shop in a CARB state will not install one.
Why the code might not be the converter
A converter that is physically intact can still throw P0420 because of a failing downstream oxygen sensor, an exhaust leak ahead of the sensor, or a misfire that has been dumping raw fuel into it. Fix those first. A new converter installed behind an unfixed misfire will fail the same way within months, and that failure is not covered by warranty.
Tell us the state the vehicle is registered in, the code you are seeing and the VIN. We quote the converter that will pass inspection where the vehicle lives, with the EO number on the quote.
Questions we get about this
It is stamped on the converter body or on a metal tag, usually near the inlet. If the original converter is still fitted it will not have an EO number, because factory converters are certified differently. Only aftermarket CARB converters carry one.
No. California requires the CARB-certified part regardless of receipts, and the smog station checks the stamp. Installing a federal converter on a California-registered vehicle can also expose the installer to penalties.
It has more precious-metal loading and has passed a stricter durability test, so in practice it lasts longer. If you tow or drive high mileage, a CARB converter can be the better buy even in a federal state.