Getting started
How to read an OBD-II code format
A five-character trouble code points you toward a system and a defined fault condition. Copy every character exactly.
Start with the letter
P indicates powertrain, B body, C chassis and U network or communication. A generic emissions reader may report only a subset of the codes an enhanced scan can retrieve.
Read the full code
In P0420, the P tells you the code family. Look up the complete value to identify the catalyst efficiency result and bank. The allocation of standardized and manufacturer-specific ranges depends on the family and range.
Keep any additional details
An enhanced scanner may show a longer value, suffix or subtype. Keep the exact display and the reporting module, then use service information for your vehicle to decode it.