OBD-II Diagnostic Trouble Codes
Look up generic OBD-II fault codes from your scan tool. Search by code (like P0420) or by fault name to see what each DTC means, common causes, and repair guidance.
9,533 generic codes · SAE J2012 standard
What are OBD-II codes?
On-board diagnostics (OBD-II) stores fault codes when a sensor or system reports a problem. Your scan tool reads these Diagnostic Trouble Codes (DTCs) after the check engine or warning light comes on.
Generic codes follow SAE J2012 and use four categories: P (powertrain), B (body), C (chassis), and U (network). The same generic code can mean slightly different things depending on your vehicle — always verify with a full diagnostic scan.
Powertrain codes cover the engine, transmission, fuel system, emissions controls, and hybrid/EV drive components.
P-codes are the most common codes drivers see when a check engine light comes on. They point to faults in how the engine runs, how fuel and air are managed, how exhaust is cleaned, or how the transmission shifts.
Generic P0xxx codes are standardized across manufacturers. A P0420 on a Ford means the same general fault type as on a Toyota — though the exact repair steps can still differ by vehicle.