5 Common OBD-II Error Codes and What They Mean

Understanding OBD-II error codes is essential for any technician. Here are the 5 most common codes you will encounter:

P0300 - Random/Multiple Cylinder Misfire

This code indicates that the engine is misfiring on multiple cylinders. Common causes include worn spark plugs, bad ignition coils, or vacuum leaks.

P0171 - System Too Lean (Bank 1)

This means the engine is running lean. Check for vacuum leaks, faulty MAF sensor, or clogged fuel injectors.

P0420 - Catalyst System Efficiency Below Threshold

The catalytic converter is not performing efficiently. This could be due to a failing converter or O2 sensor issues.