Free fault code lookup

Type any fault code. See what it meant for real owners.

Generic OBD-II codes and carmaker codes alike: which cars report it, what the car did, and whether a recall covers it, from 8,865 owner complaints filed with NHTSA. No app, no sign-up.

Try:

  • 614codes with owner reports
  • 8,865owner reports
  • 2,066generic definitions
  • 19brands, 2012 onwards

Most reported fault codes

Ranked by how many owners mentioned the code in a complaint. Codes starting with P are powertrain, C chassis, B body and U network.

How it works

  1. Type the code as it appearsAny form works: P0300, p0300, PO300, 0300 or P0300-00. The box completes it as you type and understands car names too, like "focus p03".
  2. Read what owners reportedEvery mention of that code in NHTSA complaints, grouped by car model and model year, with the owners' own words and the component they filed it under.
  3. Check for a recallRecalls that name the code, plus recalls on the same component for the same cars. Then verify your own VIN at nhtsa.gov/recalls; the repair is free.

What the first letter tells you

P 路 Powertrain (419 codes)

Engine, transmission, fuel and emissions. P0 and P2 codes are the same on every car; P1 codes mean something specific to that carmaker.

C 路 Chassis (51 codes)

Brakes, ABS, stability control, steering and suspension. C0 codes are generic; C1 and C2 are carmaker-specific.

B 路 Body (42 codes)

Airbags, seats, lighting, climate and comfort electronics. B0 codes are generic; B1 and B2 are carmaker-specific.

U 路 Network (102 codes)

Communication between the car's control modules. U0 codes are generic, often "lost communication with" a module.

Questions about fault codes

What is a fault code?

A diagnostic trouble code (DTC) is a five-character code a car stores when a sensor reading or module falls outside its limits, such as P0300 or C0020. A code reader or dealer tool shows it. The code names the system and fault type; it does not by itself say which part failed.

Where do the owner reports come from?

From complaints owners filed with the U.S. National Highway Traffic Safety Administration (NHTSA). CarHooq reads the text of every complaint for 19 US and European brands, model years 2012 onwards, and picks out the fault codes owners wrote. The counts are mentions in complaints, not how often the code occurs on the road.

What if my code is not listed?

If it is a generic OBD-II code, the search still shows its standard definition. If it is a manufacturer code nobody has reported yet, there is no page. Either way, look up your car's own problem report: it lists the symptoms and recalls other owners of the same model year reported.

Does CarHooq tell me how to fix the code?

No. CarHooq shows what owners reported and what official recall notices say. A stored code needs the freeze-frame data and a proper diagnosis, so ask a workshop to read it before anyone clears it, and check your VIN for open recalls first: recall repairs are free.

Sources

Owner reports: NHTSA Office of Defects Investigation complaint database (public domain), retrieved November 3, 2026. Generic code definitions: SAE J2012 standard wording. Recalls: NHTSA recall database. Nothing on these pages is a diagnosis. How CarHooq reports are made.