OBD-II Code Lookup
Look up the meaning of any OBD-II diagnostic trouble code (DTC). Enter a P0xxx, P1xxx, B0xxx, C0xxx, or U0xxx code to see what it means, common causes, severity, typical repair cost, and which systems it affects.
OBD-II Code Lookup
Get the system area, severity and drivability hint for any OBD-II code.
How It Works
OBD-II codes follow SAE J2012 format. The first letter identifies the system (P=powertrain, B=body, C=chassis, U=network). The first digit indicates standardized (0) or manufacturer-specific (1). The remaining three digits identify the specific fault. Some codes are universal across all OBD-II vehicles; others are brand-specific.
How to Use This Calculator
- Read the trouble code from your OBD-II scanner or the dashboard CEL flashing pattern on older cars.
- Enter the full code (e.g., P0420) into the lookup tool.
- Review the meaning, severity, and common causes.
- Diagnose the most likely cause first — usually the cheapest fix.
- Clear the code only after the repair is verified.
Worked Example
Reference Table
OBD-II code prefix legend. ProCarManuals hosts detailed code databases for specific brands — see the related guides below.
| Code prefix | System | Examples |
|---|---|---|
| P0xxx | Powertrain — generic (SAE) | P0300 misfire, P0420 cat efficiency, P0171 lean |
| P1xxx | Powertrain — manufacturer-specific | Varies by brand — check brand-specific list |
| P2xxx | Powertrain — generic newer codes | P2098 lean cylinder bank, P2197 lean trim |
| P3xxx | Powertrain — hybrid/EV codes | P3000 series — battery, motor, regen |
| B0xxx | Body — airbags, seatbelts, climate | B0001 driver airbag, B1342 ECM ROM error |
| C0xxx | Chassis — ABS, brakes, suspension | C0035 LF wheel speed sensor |
| U0xxx | Network — CAN bus, module communication | U0100 lost ECM/PCM comm |
Frequently Asked Questions
What does P0420 mean and is it expensive?
Catalytic converter efficiency below threshold on Bank 1. About 60% of the time it’s the catalyst itself ($800–1 800), 25% a failing rear O2 sensor ($80–200), and 15% an exhaust leak or rich-running engine. Always test the downstream O2 sensor before replacing the cat.
Can I clear an OBD-II code by disconnecting the battery?
Yes, but only temporarily. If the underlying fault remains, the code returns after 1–2 drive cycles. Some codes (P0420 cat, EVAP codes) take 2–4 drive cycles to come back.
Why does my Check Engine Light flash vs stay solid?
Flashing CEL = active misfire severe enough to damage the catalyst. Stop driving or drive very gently to the shop. Solid CEL = an issue exists but no immediate danger — drive normally to diagnosis.
Are P1xxx codes the same across brands?
No. P0xxx codes are SAE standardized — every brand uses them the same way. P1xxx codes are manufacturer-specific, so P1349 means different things on a Honda vs a Mazda. Look up the code for your specific brand.
Can I read codes without a scanner?
On 1996–2003 vehicles, often yes — short two pins in the diagnostic connector or cycle the key on/off, and the CEL flashes the code. On 2004+ vehicles, you need a scanner — $20 Bluetooth OBD-II adapters work with smartphone apps.
