P0301 — Cylinder 1 Misfire Detected
High severityWhat it means
The engine control unit has counted repeated misfires in cylinder 1 specifically. Because the fault is isolated to one cylinder, the cause is usually a component that serves only that cylinder, such as its spark plug, coil or injector.
Common symptoms
- Rough idle, especially at a stop
- Engine vibration and power loss
- Flashing or steady check engine light
- Fuel smell from the exhaust in severe cases
Likely causes
- Worn or fouled spark plug in cylinder 1
- Failing ignition coil on cylinder 1
- Clogged or leaking fuel injector
- Low compression (valves, rings, head gasket)
- Wiring or connector fault at the coil
What to check first
- Swap the cylinder 1 coil with another cylinder and see if the code follows
- Inspect and replace the spark plug if worn
- Compare injector behaviour across cylinders
- Run a compression test if the misfire persists
Can you keep driving?
Like all misfires, this can overheat the catalytic converter. Keep driving to a minimum until the cause is found, and stop driving if the check engine light flashes.
Frequently asked questions
What is the most common cause of P0301?
The most likely cause is: Worn or fouled spark plug in cylinder 1. Several other faults can set P0301 as well, so confirm the real cause with live data and the checks above before replacing any parts.
Can I just clear P0301 and keep driving?
Clearing P0301 with an OBD2 scanner turns the warning light off, but if the underlying fault has not been repaired the code will usually come back within a few drive cycles. Fix the cause first, then clear the code to confirm the repair worked.
How serious is P0301?
P0301 is a high-severity code. Diagnose and repair it as soon as possible, because continuing to drive can cause further damage or leave you stranded.
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