OBD-II FAULT CODE
P0301: Cylinder 1 misfire detected
CombustionGeneric powertrainThe controller has detected irregular combustion attributed to cylinder 1. Confirm the manufacturer cylinder numbering before testing.
Possible causes
Examples to investigate; this list is not a probability ranking or a diagnosis.
- Spark plug, ignition coil or wiring fault on petrol engines
- Injector or fuel-delivery fault
- Low compression or an air leak affecting the cylinder
Symptoms you might notice
- Rough idle and hesitation
- Check-engine light, which may flash during severe misfire
Diagnostic approach
- Stop safely if the lamp flashes or the vehicle runs severely rough.
- Confirm cylinder 1 location and save freeze-frame and misfire-counter data.
- Use guided ignition, injector and compression testing to identify the cause.
Save codes and freeze-frame information before clearing anything. A cleared warning light does not prove that a repair worked; the applicable monitor must run again.
Possible repairs — after testing
- Repair the fault confirmed by testing.
- Verify stable combustion and monitor completion after repair.
Related codes
This is general diagnostic orientation, not a manufacturer-specific repair procedure. A qualified technician can confirm test conditions and safe working methods.