A diagnostic trouble code identifies the system where the control module detected an abnormal condition. It rarely proves which component failed.
First: decide whether to stop
A flashing check-engine light can indicate a severe misfire capable of damaging the catalytic converter. Reduce load and stop safely. Temperature, oil-pressure and brake warnings take priority.
Capture evidence before clearing
Read stored, pending and permanent codes and save freeze-frame data. Clearing codes erases clues and resets readiness monitors.
- Record rpm, load, coolant temperature and fuel trims
- Inspect battery voltage and obvious loose connectors
- Find applicable service information and bulletins
Test the system, not the label
A lean code can come from unmetered air, low fuel delivery, an exhaust leak or incorrect sensor data. Verify the cause with live data or a physical test before buying parts.
Sources and useful tools
EPA OBD information ↗Specifications and procedures vary. Follow the owner’s manual and use a qualified technician whenever safety or diagnosis is uncertain.