About OBD2 Code Decoder

When the check engine light comes on, the first thing most people do is look up the code—P0420, P0171, or whatever the scanner shows—plus their car make. OBD2 Code Decoder exists to give you a clear, no-nonsense answer: what the code means, what usually causes it, what it might cost to fix, and where to go next.

What we do

We publish guides for hundreds of OBD2 diagnostic trouble codes, tailored by car make where it helps. Each guide explains the code in plain English, lists common causes and symptoms, suggests typical repairs, and gives a rough cost range so you can decide whether to fix it yourself, take it to a shop, or get a second opinion from a mechanic online.

Not a substitute for a mechanic

Our content is for general information only. We are not mechanics and do not diagnose or repair vehicles. Cost ranges are estimates and vary by location, shop, and parts. Always have a qualified technician diagnose and repair your vehicle when in doubt. See our Disclaimer for more.

Affiliate disclosure

We may earn a commission when you use links on this site to buy OBD2 scanners, parts, or use paid services like online mechanic advice. That support helps us keep the site running and free to use. It does not change the information we provide or our commitment to clarity and accuracy.

If you have questions about how we use data, see our Privacy Policy.