What Does Your Check Engine Code Mean?

Free OBD-II fault code lookup. Get causes, diagnostic steps, and repair costs instantly.

50+ codes covered including P0300, P0420, P0171, and more

Most Common OBD-II Codes

P0300 critical

Random/Multiple Cylinder Misfire Detected
P0420 moderate

Catalyst System Efficiency Below Threshold (Bank 1)
P0171 serious

System Too Lean (Bank 1)
P0174 serious

System Too Lean (Bank 2)
P0442 minor

Evaporative Emission Control System Leak Detected (Small Leak)
P0455 moderate

Evaporative Emission Control System Leak Detected (Large Leak)
P0128 moderate

Coolant Temperature Below Thermostat Regulating Temperature
P0401 moderate

Exhaust Gas Recirculation Flow Insufficient Detected
P0440 minor

Evaporative Emission Control System Malfunction
P0446 minor

Evaporative Emission Control System Vent Control Circuit Malfunction
P0301 serious

Cylinder 1 Misfire Detected
P0302 serious

Cylinder 2 Misfire Detected
P0303 serious

Cylinder 3 Misfire Detected
P0304 serious

Cylinder 4 Misfire Detected
P0305 serious

Cylinder 5 Misfire Detected
P0306 serious

Cylinder 6 Misfire Detected
P0307 serious

Cylinder 7 Misfire Detected
P0308 serious

Cylinder 8 Misfire Detected
P0131 serious

O2 Sensor Circuit Low Voltage (Bank 1, Sensor 1)
P0133 moderate

O2 Sensor Circuit Slow Response (Bank 1, Sensor 1)
Browse codes by vehicle make

Browse by System

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Engine
P0300-P0399
⚙
Transmission
P0700-P0799
🌿
Emissions
P0400-P0499
⛽
Fuel System
P0100-P0199

About Car Code Finder

Car Code Finder is a free OBD-II diagnostic code reference for vehicle owners and mechanics. Each code page includes a plain-English explanation, ranked probable causes, step-by-step diagnostic procedures with specific measurements, common affected vehicles, and realistic repair cost estimates.

All codes follow the SAE J2012 standard. Generic (P0xxx) codes apply to all makes and models. Manufacturer-specific codes (P1xxx, P2xxx, P3xxx) may vary by vehicle.