Smart diagnostics. Clearer solutions.

Your check engine light,
decoded in seconds.

Enter the code from your scanner and get the plain-English meaning, whether it's safe to drive, the most likely causes, and what the repair really costs.

Most searched:

P0420 P0300 P0171 P0455 P0128 P0430

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Look up a trouble code

Enter the P, B, C or U code from your scanner for meaning, severity and cost.

Start I have a symptom

Start from a symptom

Rough idle, a warning light or odd smell? Find the likely codes behind it.

Start I need a scanner

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Compare OBD-II scanners by budget, features and the make you drive.

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Reads any 1996+ vehicle

Built to actually help

More than a code definition

Thin scraper sites tell you what a code is. We tell you what to do about it — fast, honest and made for the person standing next to a running engine.

Can I drive?

A severity gauge gives you a straight answer: safe, caution, or stop.

Causes, ranked

The most likely culprits first — so you fix the right thing, not the expensive one.

Real repair cost

Honest DIY-vs-shop ranges, not a single scary number.

Make-specific notes

What the code typically means on a Toyota, Ford, Honda or Subaru.

Browse the code database

See all codes

P0420 Catalyst System Efficiency B P0300 Random / Multiple Cylinder M P0171 System Too Lean P0455 Evaporative Emission System P0128 Coolant Thermostat Below Reg P0430 Catalyst System Efficiency B P0456 Evaporative Emission System P0440 Evaporative Emission P0174 System Too Lean P0401 Exhaust Gas Recirculation P0102 Mass Air Flow P0335 Crankshaft Position Sensor C