How to find the part number on an installed part

How to Find the Part Number on an Installed Part

Quick answer: Start with your paperwork, then look at the part and the under-hood area. CARB requires exempted devices to come with an under-hood product information label, and BAR says aftermarket parts labels are affixed or stamped on the part, or installed near it.

Where to look

1. Paperwork first. Receipts, order confirmations, the box and installation instructions often list the part number. It's the easiest place to start.
2. The under-hood label. CARB's exemption procedures say this label shows the product name as listed on the EO, the EO number, and the manufacturer's name and contact information. Manufacturers may add one type of extra number: reference numbers, device numbers or kit part numbers. That one type can include several numbers.
3. The part itself. BAR's manual says aftermarket parts labels are affixed or stamped on the part, or installed near it when that isn't practical.
4. Catalytic converters. Their label follows a set format: EO number, manufacturer part number, and month and year of manufacture.
5. The manufacturer's catalog. BAR names it as a reference for EO information.

Kits have more than one number

CARB's procedures ask manufacturers to list part numbers for each kit, each part inside the kit, and each stand-alone part. So the number on one piece may differ from the kit number on your receipt. Record both.

Tips for looking safely and clearly

• Park, turn the engine off, and let everything cool before you reach in.
• Use your phone's flashlight and camera to read tight spots.
• Wipe gently. Don't peel or scrape a label.
• Write the number exactly as shown, letters and dashes included.

If the label is gone

BAR's manual says a missing or illegible aftermarket parts label doesn't by itself count against the vehicle at inspection. The inspector may proceed if the part can be confirmed by comparing the part number marked on the part with CARB's EO listings or the manufacturer's catalog. That's why the part number is worth recording.

Also note that BAR's manual says some vehicles come from the factory with tubular exhaust manifolds that look like aftermarket headers, so a tube-style part may be original.

Once you have the number, read the EO at CARB and see whether your part number appears. The Smog Check inspector makes the call at inspection.

What Showgone can and can't do here

Showgone gives every part a spot for its part number, label photos and receipt, plus a link to check the EO at CARB. Showgone isn't CARB, BAR, the DMV or a smog station, and a Showgone record isn't an official certificate.

Add this part to your free Showgone garage.

Not legal advice.

Sources

• CARB: Procedures for Exemption of Add-On and Modified Part(s) for On-Road Vehicles/Engines (adopted June 29, 2021), Sections III(b)(3) and VIII
• BAR: Smog Check Manual (April 2025), Section 1.3.2 and Appendix C (footnote 4, Catalytic Converters)
• CARB: Aftermarket parts lookup

Date checked: 2026-10-20