Catalytic converter identification and inspection

In this post I’ll go over aftermarket catalytic converters, why its important to select a catalytic converter that has been approved for your vehicle, and what smog inspectors look for when inspecting catalytic converters during a smog inspection.

This is going to be a long post, so if all you want is a quick summary, feel free to skip to the end.

… passed the smog inspection with flying colors except the tech says he can’t find a number on the cat and so he’s failing it … Is this a thing, or is the guy scamming me?

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Before removing factory original catalytic converters like these, make sure that the vehicle has been properly diagnosed and repaired.

Aftermarket Catalytic Converters

Catalytic converters contain a slurry of three rare earth metals (Platinum, palladium, and rhodium) that are used to reduce and convert harmful combustion gasses before they enter the atmosphere. All three of these metals are extremely expensive.  For example, the price of platinum on March 9, 2017, was over $947 per troy ounce.

If your vehicle is well maintained and in good working order, its catalytic converter(s) should last for the lifetime of the vehicle.

However mechanical malfunctions can damage catalytic converters and cause them to fail.  Ignition misfires are especially harmful.

Did you know?

Did you know, that a flashing check engine light usually indicates a sever catalyst damaging misfire that should be repaired without delay?

Other reasons for catalytic converter replacement include theft, incorrect diagnosis of fault codes, and the far too common practice of attempting to mask emissions control issues with new catalytic converters.

Just throw on a new catalytic converter, right?

In the past substituting a “bargain cat” for proper repairs was easier to get away with because labeling requirements were unclear, and it was often difficult for smog inspectors to identify incorrect catalytic converter applications.

When I first got my smog license, I met a customer who claimed that he made two appointments every two years; one with his muffler guy for a new catalytic converter, and one with my boss for a smog inspection. He was almost proud of the fact that he bought a new catalytic converter every two years.

It wasn’t uncommon for people to buy cheap/universal catalytic converters specifically for the purpose of “getting through” a tailpipe emissions test.  Very often those catalytic converters were so cheaply made that they might make it through a smog inspection but not much further down the road.

The worse part was that perfectly good factory parts were often replaced by low quality aftermarket catalytic converters when a simple repair was all that was necessary.

However, new catalytic converter labeling requirements adopted by the California Air Resource Board (CARB) in 2009 make catalytic converter verification much easier.

Catalytic Converter Labeling Requirements
  • Labels must be permanent and indestructible
  • Labels must be placed in a location easily readable after installation
  • Labels must use letters and numbers that are at least half an inch and readable within five feet.
  • Catalytic converters must be stamped with a directional flow arrow
  • Must include executive order exemption number (D-###-###), manufacturer part number, and date of manufacture

OEM vs. Aftermarket Catalytic Converters

OEM (Original equipment manufacturer – factory) catalytic converters are a great choice for those of us who can afford them, but very often the difference in price between a “factory cat” and an aftermarket catalytic converter can add up to hundreds of dollars (Sometimes thousands if more than one catalytic converter requires replacement).

No person shall install, sell, offer for sale, or advertise any device, apparatus, or mechanism intended for use with, or as a part of, a required motor vehicle pollution control device or system that alters or modifies the original design or performance of the motor vehicle pollution control device or system.

California Vehicle Code Vehicle Code section 27156 (c)

Aftermarket catalytic converters must be exempted from California’s anti-tampering laws in order to be legally sold and installed in the state. If an aftermarket catalytic converter is shown to be durable and meets vehicle emission control requirements, it is granted an exemption Executive Order (EO) that allows it to be installed on specific emission controlled vehicles.

If an ounce of platinum costs $947, rhodium $930, and palladium $773 an ounce, how much of each could possibly be in a catalytic converter sold for as little as forty-one dollars? The answer is, not enough to qualify for sale in the State of California!

In order to be legally sold and installed in California, a catalytic converter must undergo extensive testing to prove that it is durable and meets emission control requirements.  It’s not enough for a catalytic converter to “just get you through your next smog”, it must be built to last.

Did you know?

Did you know, that aftermarket catalytic converter installers in the State of California are legally obligated to provide you with a five year/fifty-thousand mile warranty on parts and labor?  Did you receive your warranty card?

Aftermarket catalytic converters sold in the State of California must be proven to have a minimum durability of 5 years/50,000 miles.

Catalytic Converter Inspection

Original Equipment Manufacturer Catalytic Converters

When inspecting a vehicle’s catalytic converters, the first thing we check for is  original equipment.

If a vehicle is equipped with OEM (factory) catalytic converters our job is almost complete. We still need to ensure that all catalytic converters are present, undamaged, unmodified, and installed in their original locations.

Aftermarket Catalytic Converters

There are two sets of rules that smog inspectors are required to follow when inspecting aftermarket catalytic converters:

  • Pre-OBD II Vehicles (1995 and older)
  • OBD II Vehicles (1996 and newer)
PRE-OBD II Aftermarket Catalytic Converters

When inspecting aftermarket catalytic converters installed on pre-OBD II vehicles, smog inspectors in the State of California must first follow all of the same rules that apply to OEM catalytic converters.

A word about installation:

In addition to installing catalytic converters in their original location and configuration, installers must also ensure that they follow all manufacturer guidelines.


Some catalytic converters have the word “TOP” stamped or engraved on one side (Usually on the heat shield). Very often they will come into the shop installed “upside down”.  In addition to the non-shielded side being exposed to the vehicle’s floorboard, the executive order exemption number, manufacturer part number, and date of manufacturer will not be visible.

In most cases the smog inspector inspecting the vehicle will enter “Tamper” or “Modified” for the catalytic converter, and the vehicle will fail the smog inspection.

All required catalytic converters must be present and properly installed in their original factory locations and configuration. Again, catalytic converters must not be modified or damaged.


When inspecting aftermarket catalytic converters installed on pre-OBD II vehicles, smog inspectors in the State of California must also ensure that all aftermarket catalytic converters installed on the vehicle comply with applicable labeling requirements (See above).

Unlike OBD II vehicles (Discussed below), inspectors are not required to verify specific vehicle applications when inspecting pre-OBD II vehicles; however, the catalytic converter must be approved for the vehicle category (PC 1, PC 2, T1, T2, etc).

  • PC 1 (Single Configuration) – A passenger car with single or dual exhaust that is equipped with one catalytic converter per bank.
  • PC 2 (Dual configuration) – A passenger car with single or dual exhaust that is equipped with two or more catalytic converters per bank.
  • T1 (Single Configuration) – A light duty or medium duty truck with single or dual exhaust that is equipped with one catalytic converter per bank.
  • T2 (Dual configuration) – A light duty or medium duty truck with single or dual exhaust that is equipped with two or more catalytic converters per bank.

For example:

A PC 1 passenger car can not be equipped with a catalytic converter that has been approved for T1 vehicles.

You can access CARB’s catalytic converter database at

OBD II Aftermarket Catalytic Converters (1996 and newer vehicles)

Again, OBD II aftermarket catalytic must follow the same rules regarding placement, configuration, and condition that apply to OEM and pre-OBD II catalytic converters.

In addition to those rules, OBD II aftermarket catalytic converters must be approved by CARB for specific vehicle applications.

The following information must match on all OBD II aftermarket catalytic converter applications:

  • Executive order exemption number (D-###-###)
  • Manufacturer part number
  • Model year
  • Make
  • Model
  • Engine size
  • Engine Family Number (Also referred to as engine test group)
CARB Catalytic Converter Database

When it comes to inspecting aftermarket catalytic converters (Especially on OBD II vehicles), CARB’s catalytic converter database is the smog inspectors bible.

After selecting a vehicle’s manufacturer, model year, model, and engine size from the database’s drop down menus, the database returns a list of all CARB approved catalytic converters for the selected vehicle.

Your muffler guy may make a lot of reasonable arguments, but if a catalytic converter is not CARB approved for your vehicle it will not pass a California state smog inspection.

To determine the correct catalytic converter part number for your vehicle, you will need its make, model, model year, engine size and test group/engine family designation.

Test Group Name (Engine Family Number)

The engine family or test group is the one field that seems to create the most confusion among installers, consumers, and even some smog inspectors.

Emissions control information label

All vehicles sold in the United States have a unique drive-train identifier called the “Test Group” or “Engine Family Number”. This number allows owners, parts suppliers, and service providers to determine specifications and installed emissions control equipment of motor vehicles. Because many vehicles may have several different configurations, this number will provide specific information about the emissions control system and exact standards that a vehicle was designed to meet.

In many cases a single character in the test group will be the determining factor between a passing catalytic converter, and a failed smog inspection.

Federal/EPA Only

On Federal/EPA certified vehicles (Those that are not California emissions certified), EFN does not need to match since only CARB approved EFNs are listed in the database.  However, all other requirements apply.

Q. Federal vehicles are not listed in California application catalog. How do I determine what catalytic converter to install on a federal vehicle?

A. Find a catalytic converter exempted for a California vehicle that is of the same make, model, and model year as the federal vehicle, except for the engine family. Install the catalytic converter on the federal vehicle and make a note on your invoice and warranty card that it is a federal vehicle.

CALIFORNIA AIR RESOURCES BOARD FREQUENTLY ASKED QUESTIONS New Aftermarket Catalytic Converters Installation Requirements

 Application Type

Application type can be 2WD, AWD, 4WD, ALL, etc. We don’t see this very often, but it is possible for a catalytic converter to be approved for two wheel drive applications, but not four wheel drive, or the other way around.

Part Manufacturer

The manufacturer of the catalytic converter.

Manufacturer Part Number

The catalytic converter’s manufacturer part number.

The part number must be an exact match.


82633 and 82633R are not a match.

Executive Order

The catalytic converter’s executive order exemption number.

By clicking on the executive order number in the list, you can view a PDF of the actual executive order for the exemption.

The executive order document will list information regarding specific vehicles and manufacturer part numbers covered by the executive order.

Total Converters

The total number of catalytic converters that should be installed on the vehicle.

Catalyst Location

Not all catalytic converters installed on a vehicle serve the same function. When inspecting aftermarket catalytic converters, it is important for an inspector to ensure that all catalytic converters are installed in the correct location.

Rescinded and Withdrawn

Affected converters sold on or before their rescission or withdrawal date, are legal for use and installation in California. Affected converters sold after their rescission or withdrawal date, are not legal for use or installation in California.

You may have noticed that the catalytic converter database indicates that some executive order numbers are Rescinded, while others are listed as Withdrawn. 


An executive order exemption that is listed as Rescinded is one that has been rescinded (cancelled) by CARB.


An executive order exemption that is listed as Withdrawn is one that has been withdrawn by the manufacturer.

In either case, rescinded or withdrawn, it is not legal to advertise, sell, or install affected catalytic converters after the date of rescission or withdrawal.

You can find the date of rescission or withdrawal by clicking on the executive order number in the catalytic converter database listing. The applicable date will appear stamped across the executive order PDF document.

Toyota Sequoia and Tundra Pickup Trucks

CARB goofed a few years ago and published the wrong information for certain Toyota Sequoia and Tundra pickup trucks.  As a result Sequoia’s and Tundra’s failed smog inspections, and the wrong number of catalytic converters were installed based on CARB’s information.

Fortunately CARB decided to play fair. CARB is allowing use of catalytic converters installed based on the wrong information as long as the installation occurred during the affected period.

Click here for more information.


This was a long post, so let’s summarize.

  1. Before you replace a catalytic converter, especially an OEM/factory catalytic converter:
    • Make sure that your vehicle has been properly diagnosed, and that the catalytic converter has actually failed.
    • Repair all other mechanical issues that may have damaged the original catalytic converter.
    • Do not use a new catalytic converter as a substitute for proper emissions repairs.
  2. Maintain the original exhaust/catalyst configuration.
    • Do not add or subtract catalytic converters.
    • New converters must be installed in the original catalytic converter locations.
    • Do not modify existing or new catalytic converters.
  3. Catalytic converters must be installed according to manufacturer specifications.
    • Observe direction of flow.
    • Do not install replacement catalytic converters upside down.  If a top is indicated, that should be on top.
    • If a catalytic converter is installed incorrectly, the vehicle will not pass a California smog inspection and a smog certificate will not be issued.
  4. Install catalytic converters that are CARB approved and legal for sale and use in California.
    • California legal catalytic converters will comply with CARB labeling requirements
    • If an aftermarket catalytic converter does not comply with CARB labeling requirements, the vehicle will not pass a California smog inspection, and a smog certificate will not be issued.
  5. Pre-OBD II Vehicles (Model year 1995 and older):
    • Catalytic converter must be approved for vehicle class (PC1, PC2, T1, T2)
    • If a catalytic converter is not approved for the vehicle’s class, the vehicle will not pass a California smog inspection, and a smog certificate will not be issued.
  6. OBD II Vehicles (Model year 1996 and newer):
    • The catalytic converter’s executive order exemption number, and manufacturer part number, must be approved for the vehicle’s:
      • Model Year
      • Manufacturer/Make
      • Model
      • Engine Family Number (Test group)
      • Engine Size
      • Location on Vehicle

If any of the above do not match, the vehicle will not pass a California smog inspection, and a smog certificate will not be issued.

Catalytic converter visual inspections constitute just one part of the California smog inspection, but if you have made it this far, you now know that it takes a lot of knowledge to do it right.

6 Replies to “Catalytic converter identification and inspection”

  1. Josiah M Callison

    On my aftermarket cat the EO for it is older than the one that says it’s ok for my vehicle so it isn’t stamped with the one I need. Shops won’t let me use it, is my only remedy replacement ?

  2. Peter

    Hi, my stock catalytic converter doesn’t even have any markings AT ALL (it’s off the car at the moment). How does the inspector know it is the OEM version and not an aftermarket converter that might have no markings either? Have had no problem so far, but just wondering. Also means I could put on an aftermarket version with no markings once this one goes out.

    • dewok

      Hi Peter,

      Many factory catalytic converters don’t have any obvious markings. Technicians can usually identify aftermarket catalytic converters visually by either a different shape and/or non-factory welds. Since 2010 there are standardized markings on all California approved aftermarket catalytic converters: CARB# (D-xxx-xx), Part #, and production date.

      • Reggie Beard

        Hey I live in Jersey and i have a California emissions 3003 Honda accord v6 I. Excellent condition. I failed inspection because my engine light was on because of the catalytic converters.. I replaced them. Still failed and found out that I need cats for California emissions. I am having a very hard tim trying to find them for this car.

        • dewok

          Hi Reggie,

          If you order factory Honda catalytic converters based on your VIN number, you will be fine.

          If you want to install aftermarket converters, visit this website.

          Make sure you note the “Engine Family” or “Test Group” from your under hood emission label. You must chose a converter that matches your vehicle’s engine family.

  3. lorenzo

    hi my catalytic have only CA/TA 200-200 (front ) OB 2
    i wanted know is it the part number for boths ?


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