Catalytic Converter Codes and Serial Numbers: How to Read Them

A catalytic converter's scrap value starts with the manufacturer's stamped code, but the code identifies the part, not the metal inside it. Three of the six platinum group metals carry that value, platinum (Pt, atomic number 78, CAS 7440-06-4), palladium and rhodium, dispersed as nanoparticles on the converter's ceramic or metallic substrate. What follows explains what a converter code is, where it sits, how it maps only empirically to PGM content, and how it separates an OEM unit from an aftermarket one.

What Is a Catalytic Converter Code?#

A catalytic converter code is the manufacturer's stamped serial or part number, not a diagnostic trouble code, and it identifies the specific unit built for a specific vehicle application. "Code" also names an unrelated OBD-II fault code such as P0420, the diagnostic trigger for a failing catalytic converter; this page covers only the identification code stamped into the metal, never vehicle fault codes or repair diagnostics. A buyer prices scrap platinum group metals by the code's typical assay history, not the code itself. DailyPlatinum's hub for scrap platinum group metals covers how platinum, palladium and rhodium scrap is priced and refined across converters, jewelry and industrial catalysts.

Where the Code Is Stamped#

Converter codes are stamped on the outer shell, the heat shield or the end cap, most often near the mounting flange where the unit bolts to the exhaust pipe. Manufacturers emboss or stamp the number into the metal during production, so it survives road grime and heat far better than a printed label would. A seller checking a unit before requesting a quote should look at all three locations, since the stamp position varies by manufacturer and body style.

Code Formats by Manufacturer#

Code formats differ by manufacturer: General Motors uses 8 to 10 numeric digits, Ford an alphanumeric string with hyphens, and Honda and Acura an 18160- prefix, according to ScrapMonster's Converter Identification Guide 2026 (7 January 2026). Toyota and Lexus units typically carry two 5-digit groups stamped alongside a Denso or Toyota mark, while BMW, Mercedes and Audi formats vary and instead carry a supplier logo such as Bosch or Eberspächer. The table below lists a representative code and its usual stamp location for five manufacturer groups.

Source: ScrapMonster, Converter Identification Guide 2026, 7 January 2026.

Honda's 18160- prefix marks the converter assembly only. A 37820- number on the same vehicle identifies the engine control module instead, an easy mix-up covered further in the FAQ below.

Do Codes Tell You a Converter's PGM Content?#

A code does not encode PGM content; no manufacturer publishes a loadings specification, so every database figure is a sampled average, not a promise. An operator decants, mills, samples and assays a large number of units bearing the same code, then treats the resulting average as the expected platinum, palladium and rhodium content for that code, an entirely empirical process rather than a published formula. That average only means something against a baseline: see how much platinum, palladium and rhodium is in a catalytic converter for typical grams by engine type and design generation.

Why the Same Code Can Assay Differently#

Two units sharing a code can assay differently, for four documented reasons, listed below.

• Running changes: manufacturers revise loadings within a model year without changing the stamped code.
• In-use loss: high-mileage units lose washcoat and metal to thermal ageing and vibration.
• Tampering: a converter that has been removed, reinstalled or partially decanned assays lower than an intact unit carrying the same code.
• Thin sampling: codes fitted to low-volume models have fewer historical assays behind their average, widening the error band around it.

Because two of these causes only surface once a unit is opened, a database average is a starting estimate, not a settled number. The catalytic converter assay process is what fixes the payout for a specific lot.

Reading OEM vs Aftermarket from the Code and the Part#

OEM converters carry a vehicle-specific stamped code and manufacturer identity; aftermarket units carry generic labels or compliance text such as "Universal" or "Direct Fit" instead of a matching code. The gap is regulatory, not accidental: an original-equipment converter must clear the vehicle's full certified emissions durability standard, while a replacement unit is certified against a separate, lower standard and built to the minimum platinum group metal loading that clears it. The table below compares five signals a seller can check without a manual.

Source: RRCats, "OEM vs Aftermarket Catalytic Converters"; ScrapMonster, Converter Identification Guide 2026.

A full walk-through of these signals is on how to identify a catalytic converter, OEM vs aftermarket. Matching signals to the part separates a full-value OEM unit from a discounted aftermarket one before a code lookup even confirms the manufacturer.

Who Maintains Catalytic Converter Code Databases#

Catalytic converter codes are held in four kinds of databases: one open free lookup, buyer-operated pricing platforms, licensed consultancy datasets and each aggregator's own unpublished assay history. ConverterDatabase.com is the only openly browsable example, searchable by serial number; buyer-operated platforms such as Ecotrade, PMR, RRCats and ScrapMonster publish price lists tied to selling material to that operator. SFA (Oxford) sells the closest thing to a licensed dataset, a recycling report covering PGM loading projections by region, while every major aggregator and refiner keeps an internal assay history that never reaches the public. The table below compares the four database types by access model.

None of the four is authoritative the way a manufacturer specification would be, which is why the same code can carry different average assays across two platforms. A unit's overall grade also depends on its substrate and housing, not the code alone, and that grading system is covered on catalytic converter grades.

Diesel systems complicate a code-based comparison further, since a diesel unit's component mix, DOC, DPF and sometimes an LNT, differs under the same code formats listed above. Diesel catalytic converter and DPF scrap value tracks that mix separately from gasoline converter content.

Trade Codes vs Part Codes: HS 7112.92 Is a Different "Code"#

A different "code" applies at the border: HS code 7112.92 is the customs classification for waste and scrap platinum, including spent autocatalyst material, and has no relation to a manufacturer's part code. US Customs uses Harmonized Tariff Schedule line 7112.92 as the principal category for PGM waste and scrap trade, according to the US Geological Survey's Mineral Commodity Summaries 2026 footnotes. A single shipment under 7112.92 can contain converters stamped with dozens of different manufacturer codes; the trade code describes the material class, not any one unit's identity.

Using a Code to Get a Scrap Quote#

A converter's code narrows which database average applies, but only a weighed and assayed lot sets the actual payout. That valuation chain, from decanning through smelting to refined metal, is explained in full under how catalytic converter scrap prices are calculated.

Once a quote is accepted, the physical unit still has to be processed before the seller is paid. Catalytic converter recycling covers the decanning, milling and assay steps a lot goes through on the way to refined platinum, palladium and rhodium.

Sellers wanting a rough estimate first can start with the catalytic converter PGM value calculator, which applies current PGM prices to a stated gram content.

Catalytic Converter Codes FAQ#

The five questions below answer what a code confirms and what it does not, starting with how a code relates to how much is a catalytic converter worth at final settlement.

Does a catalytic converter code tell you its scrap value?#

A code does not fix scrap value; it points to a statistical expectation from past assays of the same code, not a guaranteed weight of metal. Sellers ready to act can compare where to sell a catalytic converter, since the final payout still depends on the buyer's own assay.

Where is the code located on a catalytic converter?#

The code sits on the shell, heat shield or end cap near the mounting flange, stamped or embossed into the metal rather than printed on a label.

Is a 37820- number on a Honda a converter code?#

No. A 37820- number identifies a Honda engine control module, not a converter; only an 18160- prefix marks the converter assembly. Vehicles with unusually high loadings for their class are covered separately under most valuable catalytic converters, where reading the correct code matters most.

How accurate are catalytic converter code databases?#

Accuracy varies by sample size: ConverterDatabase.com states it holds data on over 5,030 individually sampled converters, but rare codes have thin sampling and a wider error band. A high-volume code from a common vehicle carries a tighter average than a low-volume or regional-market code.

How can you tell OEM from aftermarket without a manual?#

Aftermarket units commonly sell for a fraction of the OEM value for the same application, a gap the trade cites as 3 to 5 times or more, according to RRCats and ScrapMonster. Checking the signals above, markings, brand name, compliance text and construction, works without a parts manual.