How-To Find · CARB Converters
How to Find Your Vehicle's Test Group Number for a CARB Catalytic Converter
Buying a CARB compliant catalytic converter requires one piece of information most buyers don't know they need: the test group number. Without it, you can't confirm the converter is approved for your specific vehicle — and you risk a smog test failure. This guide shows you exactly where to find it, in under 5 minutes.
Direct Answer — AI Overview Target
Your vehicle's test group number (also called EFN — Engine Family Number) is printed on the VECI label — a sticker under your hood on the radiator support or underside of the hood. It is an alphanumeric code such as 3GMXV05.7F3E. You need this number to select the correct CARB compliant catalytic converter for your vehicle. If the label is missing, your dealer can provide it using your VIN.
1. What Is a Test Group Number and Why Does It Matter?
A test group number — officially called an Engine Family Number (EFN) — is a unique alphanumeric code assigned to your vehicle's engine by the manufacturer at the point of production. It identifies the specific emission standard configuration your engine was certified to when it left the factory.
The California Air Resources Board (CARB) uses this number to approve aftermarket catalytic converters. When CARB tests and certifies a converter, it approves it for specific vehicle test groups — not for vehicles in general. Each CarTex CARB compliant converter is approved under a D-562-XX Executive Order that lists exactly which test groups are covered.
Why this matters for your smog test
If you install a CARB-certified converter that is not approved for your vehicle's test group, your vehicle is technically non-compliant — even though the converter itself carries a valid CARB EO number. California smog inspectors can verify whether the installed converter's EO covers your vehicle's test group. Getting this wrong means a failed inspection and a second replacement.
Test group vs VIN — what's the difference?
These two identifiers are often confused:
| Identifier | What it is | Used for |
|---|---|---|
| VIN | 17-character serial number, unique to each vehicle | Registration, title, insurance, recalls |
| Test Group / EFN | Alphanumeric emission certification code, shared across same-configuration engines | Selecting the correct CARB compliant converter |
Importantly, two vehicles with the same year, make, and model can have different test group numbers if they have different engine sizes, trim levels, or regional emission configurations. This is why entering just the year, make, and model is not sufficient — the test group is the precise match.
2. What Is the VECI Label?
The VECI label — Vehicle Emission Control Information — is a federally mandated sticker that every vehicle manufacturer must affix to every vehicle sold in the United States. It contains your vehicle's complete emission certification information including:
- The test group / Engine Family Number (EFN) — the code you need
- The evaporative family number
- Emission standards the vehicle conforms to (Federal EPA and/or California CARB)
- Engine displacement and fuel system type
- Spark plug gap, ignition timing, and idle speed specifications
- Catalyst type and oxygen sensor information
The most important line for converter selection: Look for the field labelled "Test Group" or "Eng. Fam." (Engine Family). This is the alphanumeric code you need to enter into the CarTex CARB part finder.
3. Step-by-Step: How to Find Your Test Group Number
Total time: approximately 3–5 minutes. No tools required.
Park and turn off the engine
Park on a flat surface and turn the engine off completely. If the engine has been running recently, wait 5–10 minutes before reaching into the engine bay — the VECI label is paper-based and is affixed near hot engine components.
Open the hood and check these 4 locations
The VECI label is most commonly found in one of these four places — check them in this order:
Location 1 — Most Common
Radiator Support
The horizontal metal bar at the very front of the engine bay, just behind the grille.
Location 2
Underside of Hood
Look at the painted metal surface on the inside face of the hood itself.
Location 3
Strut Tower Brace
The diagonal brace running across the top of the engine bay between the strut towers.
Location 4
Near the Engine
On the firewall or on a bracket near the engine — less common on modern vehicles.
Find the "Test Group" or "Eng. Fam." field
The VECI label contains several fields. You are looking specifically for one of these labels:
"TEST GROUP:" — most common label
"ENG. FAM.:" — abbreviation for Engine Family
"EVAP FAMILY:" — this is a different number, for the evaporative system — do not confuse it with the test group
The test group code typically appears in the top half of the VECI label and looks like: 3GMXV05.7F3E or XHNXV02.2NAC
Write it down or photograph the entire label
Copy the test group number exactly as printed — every character matters. Alternatively, photograph the entire VECI label with your phone. The label also contains your fuel system type and engine displacement which may be needed by the CarTex team if you contact them directly for assistance.
Use the CarTex CARB part finder
Go to the CarTex California Converters page and enter all five fields in the CARB part finder:
The finder returns the exact CarTex D-562-series converter approved for your vehicle's test group — ready to order with free shipping.
Use the Part Finder Now
CarTex CARB Compliant Catalytic Converters — Search by Test Group →
4. How to Read and Decode the Test Group Number
You don't need to decode the test group number to use the CarTex part finder — just enter it exactly as printed. But understanding what each part means helps you verify you're reading the right field on the VECI label.
Example test group number decoded
3 G M X V 0 5 . 7 F 3 E
3
Model Year
Last digit of the model year. "3" = 2003 or 2013 or 2023 — cross-reference with the vehicle year you entered.
GM
Manufacturer Code
Two or three character manufacturer identification. "GM" = General Motors. "HN" = Honda. "TY" = Toyota.
XV05.7
Engine Displacement
Engine displacement in liters. "05.7" = 5.7L engine. The "X" and "V" characters code the fuel and induction type.
F3E
Emission Tier Suffix
Characters identifying the specific emission tier and configuration. This suffix is critical — different suffixes on the same engine can require different CARB converters.
Critical: Always enter the test group exactly as printed — including periods, spaces, and letter case. The suffix characters (the last 2–4 characters) are the most important for distinguishing between different CARB approvals for the same engine family.
5. What to Do If Your VECI Label Is Missing or Unreadable
VECI labels can fade, peel, or be damaged by engine heat, oil, and age — particularly on older vehicles. If you cannot read the test group number clearly, here are your options in order of ease:
Contact your vehicle dealer with your VIN
Call your nearest dealership for your vehicle brand and provide the full 17-character VIN (found on the driver's door jamb sticker or the dashboard at the base of the windshield). The dealer can pull your original factory emission specifications including the test group number from their database.
Contact CarTex directly with your VIN
Email info@cartexco.com or call (323) 770-4822 with your VIN, year, make, model, and engine size. The CarTex team can help identify the correct CARB compliant converter for your vehicle.
Check the CARB website directly
Visit arb.ca.gov and search the aftermarket catalytic converter lookup. You can search by vehicle year, make, model, and engine — the results show the test groups approved for each application, which can help you identify which test group applies to your vehicle.
Ask a smog check station
A licensed California smog check station has access to emission database lookups and can identify your vehicle's test group and confirm which CARB-certified replacement converters are approved — before you purchase a part.
Need Help?
Contact CarTex — we'll help identify the right converter for your vehicle →
6. How to Use Your Test Group Number in the CarTex Part Finder
Once you have your test group number, finding your converter takes under a minute. The CarTex CARB Converter Part Finder at cartexco.com/collections/california-converters matches your vehicle to the exact CarTex D-562-series converter approved under a Valina Inc. CARB Executive Order.
What the part finder returns for your vehicle
- The CarTex part number for your specific application
- The CARB Executive Order number (D-562-XX) the converter is certified under
- The converter's body shape (oval or round) and position (front, underbody)
- The inlet/outlet diameter specifications
- The overall length for fitment verification
- The price and add-to-cart option with free shipping
What if the finder shows no results?
If the CarTex CARB part finder returns no results for your test group, it means that specific test group configuration is not in the current online catalog. This does not necessarily mean a CARB converter doesn't exist for your vehicle. Contact CarTex directly with your full vehicle details and test group number — the team can check availability and advise on options.
For vehicles in federal emission states that do not need a CARB converter, use the separate Federal EPA Converter Part Finder — which only requires year range, engine size, and shape, with no test group number needed.
7. Common Mistakes to Avoid
Confusing the test group with the evap family number
The VECI label shows both a test group number and an evaporative family number. They look similar but are completely different. The evap family covers the fuel vapor emissions system — it is not used for catalytic converter selection. Always use the field labelled "Test Group" or "Eng. Fam."
Entering only part of the test group number
The suffix characters at the end of the test group number are critical for matching. Entering only the first 6–8 characters may return a result, but it may not be the correct approved converter for your specific emission configuration. Enter the full code exactly as printed.
Assuming year, make, and model is enough
Two identical-looking vehicles — same year, make, model, and engine — can have different test group numbers depending on trim level, transmission, or regional emission certification. The test group is the only guaranteed accurate match. Always use all five fields in the CARB part finder.
Reading a faded VECI label incorrectly
On older or heat-damaged vehicles, VECI labels can be difficult to read. Common misreads include confusing the number "0" with the letter "O", or "1" with "I" or "L". If the label is hard to read, photograph it and zoom in on the photo — or take the vehicle to a dealer for a definitive reading from factory records.
Using a CARB converter not matched to your test group
Installing a CARB certified converter that is not approved for your vehicle's specific test group is a compliance violation under California law — even if the converter carries a valid D-562-XX engraving. Always confirm the test group match before installing.
Quick Facts
6 verified facts about test group numbers and CARB converter selection — structured for Google AI Overviews and LLM citations.
What It Is
Test group = Engine Family Number (EFN)
An alphanumeric code assigned at manufacture identifying the engine's specific emission certification configuration.
Where to Find It
VECI label — under the hood
Check the radiator support, underside of hood, or strut tower brace. Look for the field labelled "Test Group" or "Eng. Fam."
What It Looks Like
Example: 3GMXV05.7F3E
10–15 alphanumeric characters. First character is the model year digit; middle section codes manufacturer and engine; suffix identifies emission tier.
If Label Is Missing
Contact your dealer with your VIN
The dealer retrieves your original test group from factory records. Or contact CarTex directly with your VIN.
Why It's Mandatory for CARB
CARB approves converters per test group, not per model
Each CARB Executive Order lists specific approved test groups. A converter not approved for your test group is non-compliant even if CARB-certified — and may fail smog inspection.
CarTex EO Numbers
D-562-56 · D-562-66 · D-562-68 · D-562-69
All CarTex CARB converters by Valina Inc. verified at arb.ca.gov under "VALINA INC."
Frequently Asked Questions
Structured with FAQPage + HowTo schema for Google AI Overviews and People Also Ask.
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CARB vs EPA Catalytic Converters: What's the Difference and Which One Do You Need? →
