P0301 Cylinder 1 misfire detected
What P0301 means
The engine computer detects misfires from small dips in crankshaft speed and can tell which cylinder caused them. P0301 means cylinder 1 is not burning its fuel properly. Unburned fuel then reaches the catalytic converter, which can overheat if the misfire continues.
P0301 is a generic SAE J2012 code: it means the same on every make. The exact cause still depends on the car, so read the freeze-frame data before replacing parts.
At a glance
- Severity
- High
- Typical repair cost
- 40–400 €
- Workshop time
- 0.3–4 h
- Repair difficulty
- Easy
- DIY possible
- Yes
- Check engine light
- Yes
- Affects emissions test
- Yes
Parts and labour at an independent workshop in Europe. Main dealers charge more; the cause decides the bill, not the code.
Symptoms
- Check engine light on or flashing
- Rough idle and vibration
- Hesitation when accelerating
- Higher fuel consumption
Common causes
- Worn or fouled spark plug in cylinder 1
- Faulty ignition coil for cylinder 1
- Clogged or faulty injector for cylinder 1
- Vacuum leak near cylinder 1
- Low compression in cylinder 1 (valves or piston rings)
Can I keep driving with P0301?
Have it checked today or tomorrow. If the check engine light flashes, avoid driving, because the catalytic converter can be damaged quickly.
What to check first
- Swap the cylinder 1 coil with another cylinder, clear codes and see if the misfire follows
- Inspect and replace the spark plug if worn, cracked or oil-fouled
- Check the injector wiring and operation for cylinder 1
- Do a compression test if ignition and fuel are good
Related codes
- P0300 Random/multiple cylinder misfire detected
- P0302 Cylinder 2 misfire detected
- P0303 Cylinder 3 misfire detected
- P0304 Cylinder 4 misfire detected
- P0305 Cylinder 5 misfire detected
- P0306 Cylinder 6 misfire detected
- P0307 Cylinder 7 misfire detected
- P0308 Cylinder 8 misfire detected
Data: TORKO fault-code catalogue, built on OBDex (CC0-1.0) and reviewed against workshop practice. Informational only — it does not replace a diagnosis by a mechanic.
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