Car OBD Codes.
Complete OBD-II diagnostic trouble code reference. Look up any code to find its meaning, symptoms, causes, and fixes.
🔍
Browse by Code Type
Most Common Trouble Codes
P0171System Too Lean (Bank 1)P0420Catalyst System Efficiency Below Threshold (Bank 1)P0300Random/Multiple Cylinder Misfire DetectedP0440Evaporative Emission Control System MalfunctionP0172System Too Rich (Bank 1)P0301Cylinder 1 Misfire DetectedP0455Evaporative Emission Control System Tank Detected (gross leak)
Frequently Asked Questions
View all →What is OBD-II?
OBD-II is the standardized vehicle diagnostic system required in all US cars since 1996 that monitors emissions and engine performance.
What is the difference between OBD-I and OBD-II?
OBD-I (1981-1995) used manufacturer-specific systems, while OBD-II (1996+) standardized connectors, codes, and protocols across all brands.
What does the Check Engine Light mean?
The Check Engine Light means the OBD-II system detected an engine, transmission, or emissions problem. A flashing light means stop driving immediately.
What cars have OBD-II?
All US cars since 1996, all European gasoline cars since 2001, and diesel cars since 2003 have OBD-II.