Why an EO number alone doesn't show your vehicle is covered

Why an EO Number Alone Doesn't Show Your Vehicle Is Covered

Quick answer: An EO covers specific parts on specific vehicles, so an EO number on a part doesn't by itself show that the EO includes your vehicle or your exact part. To research coverage, compare your part number and vehicle details with what the EO actually lists.

Why the number isn't the whole story

An EO allows a modification to be installed on specific emission-controlled vehicles. Under CARB's exemption procedures, manufacturers apply with a list of the vehicles or engines to be covered and the part numbers for each kit and part. Manufacturers also may not market a device for any application other than those listed on the EO.

BAR's Smog Check Manual shows how detailed this gets. For aftermarket catalytic converters, inspectors use the EO number and the part number together to check that the part is listed for that specific vehicle configuration, such as year, make, model, engine, GVWR and fuel type. This configuration check applies to OBD II vehicles only.

CARB's enforcement advisory sums it up for owners: buy, install and use performance products that have a CARB EO for your own specific vehicle model.

Gaps worth researching

• Part number: Does the EO list the exact part number on your part, not just the product line?
• Vehicle details: Do your model year, model and engine all appear?
• Install conditions: When an install requires re-routing hoses or belts, or changing tune-up specifications, CARB requires the label (or a second label) to describe those changes. Were they followed?
• Type of EO: CARB also issues EOs that certify new vehicles. Make sure you're reading the part's EO.

Practical steps

1. Write down the part number exactly as it appears on the part or label.
2. Write down your vehicle's year, make, model and engine, and photograph the underhood emission control label, which shows your test group or engine family number.
3. Read the EO at CARB.
4. Compare your details with the EO, line by line.
5. Save a copy of the EO with the date you checked.
6. Unclear? Ask CARB at (800) 242-4450. For inspection questions, the Smog Check Referee can be reached at (800) 622-7733.

The inspector at your Smog Check makes the call on your vehicle, and the Referee helps with disputes and unusual cases.

What Showgone can and can't do here

Showgone lets you keep your part number, vehicle details and saved EO side by side, with a link to read the EO at CARB. Showgone isn't CARB, BAR, the DMV or a smog station, and a Showgone record isn't an official certificate or a coverage decision.

Add this part to your free Showgone garage.

Not legal advice.

Sources

• CARB: Aftermarket, Performance, and Add-on Parts
• CARB: Procedures for Exemption of Add-On and Modified Part(s) for On-Road Vehicles/Engines (adopted June 29, 2021), Sections III(b), VIII and IX
• BAR: Smog Check Manual (April 2025), Appendix C, Catalytic Converters
• CARB Enforcement Advisory #292 (July 10, 2020), Consumers section
• CARB: California Racing Vehicles: Aftermarket Parts & Executive Orders
• CARB: Locating vehicle "Test Group" or "Engine Family" Number
• BAR: On-Board Diagnostic Test Reference (Referee contact)

Date checked: 2026-10-20