About Car Code Finder

Car Code Finder is a free automotive diagnostic reference covering more than 13,000 OBD-II, diesel, EV, and heavy-equipment fault codes. When a check engine light comes on, our goal is simple: help you understand what the code actually means, how serious it is, and what it typically takes to fix — in plain English, before you spend money at a shop.

What we cover

Every code page includes a plain-English explanation, a severity rating, the common causes, step-by-step diagnostic guidance, and — where available — vehicle-specific repair notes with part recommendations. Our catalog spans:

  • Gas vehicles (1996 and newer) — the full OBD-II P, B, C, and U code set.
  • Diesel trucks — Cummins, Duramax, Power Stroke, PACCAR, Detroit Diesel, and more, including J1939 fault codes.
  • Electric vehicles — Tesla and Chevrolet Bolt EV diagnostic codes.
  • Commercial and heavy equipment — generators, aerial lifts, telehandlers, compressors, and agricultural machinery.
  • A growing Spanish-language section covering the full diesel and heavy-equipment catalog, for the many owner-operators and technicians underserved by English-only resources.

Who it's for

We build for DIY mechanics, vehicle owners, fleet operators, and working technicians — anyone who wants to understand a diagnostic trouble code well enough to make an informed decision, whether that's a driveway repair or a smarter conversation with a shop.

Our commitment to accuracy

Diagnostic information is only useful if it's correct. We write from established, documented repair knowledge and cite sources where we can. We are deliberate about not inventing part numbers, codes, or specifications. Where a code or fix is vehicle-specific, we say so — because a cause on one vehicle may not apply to another.

That said, all content is for general informational purposes only and is not a substitute for hands-on diagnosis by a qualified mechanic. See our Terms of Service and Disclaimer for the full picture.

How we keep it free

Car Code Finder is free to use and supported by advertising and affiliate partnerships. When our diagnostic guides recommend a scan tool, replacement part, or maintenance product, those links may earn us a commission at no additional cost to you. We only recommend products that fit the problem the page is about. For details, see our Disclaimer.

Who runs it

Car Code Finder is owned and operated by Keystone Logic Systems LLC, a United States-based company. Questions, corrections, partnership inquiries, or a code you'd like us to add? We'd genuinely like to hear it — reach us through our Contact page.