P0301 Check Engine Code
Cylinder 1 is the one dropping the ball - fuel is not burning cleanly in that hole alone. P0301 is cylinder 1 misfire detected, which is narrower than P0300 (random or multiple). Most of the time it is ignition: spark plug, coil, or boot on that cylinder, sometimes the injector. A flashing light with P0301 still risks catalytic converter damage from unburned fuel, so the urgency stays high even when the scan tool already named the cylinder.
Symptoms
- Check engine light - may flash under load with active misfire
- Rough idle or stumble you can feel at low speed
- P0301 alone or with P0300
- Recent tune-up where cylinder 1 plug or coil was disturbed
- Fuel trim normal or lean on the bank that includes cylinder 1
Can I keep driving with a P0301 code?
- Steady light with mild roughness - gentle drive to diagnosis soon.
- Flashing light - reduce load immediately; same urgency as P0300.
- Do not swap coils randomly without confirming cylinder 1 counts on a scan tool.
Often confused with
- P0300 random misfire - multiple cylinders or unstable counts
- P0302 through P0308 - other cylinders; a swap test isolates coil-related faults
Common causes
- Failed coil-on-plug or spark plug on cylinder 1
- Cracked plug insulator or wrong plug gap
- Injector restriction on cylinder 1
- Low compression on cylinder 1 (after ignition is ruled out)
- Vacuum leak affecting cylinder 1 runner on some intakes
If you ignore it
- Catalyst damage from cylinder 1 misfire under load
- Coil failure spreading heat to neighboring components
- Fouled plug becoming hard to remove
Repair overview
- Confirm misfire counts on cylinder 1 with a scan tool
- Inspect plug and coil; swap coil test when safe and applicable
- Injector and compression tests when ignition looks good
What happens next
- Call with whether the light flashes and whether roughness is constant or only when cold.
- We isolate cylinder 1 on scan data before quoting plugs, coils, or deeper work.
Questions
What does P0301 mean?
P0301 is Cylinder 1 Misfire Detected. Cylinder 1 is the reference cylinder for bank 1 on your engine. The computer counted enough misfire events on that cylinder to store a code.
Can I swap the coil to test P0301?
On some engines, moving the coil to another cylinder and watching misfire counts move with it speeds diagnosis. We do that when the design allows - instead of guessing at parts.
Is P0301 an emergency?
A steady light with mild roughness - get it scanned soon. A flashing light means the engine is misfiring while you drive; drive gently and come in quickly to protect the catalytic converter.