OBD-II diagnostic trouble code
P0301Caution
Cylinder 1 Misfire Detected
The engine computer has pinpointed the misfire to cylinder 1 specifically — unlike the random/multiple misfire code, this one is isolated to a single cylinder, which usually points to something local to that cylinder rather than an engine-wide problem.
Symptoms
- A distinct, rhythmic shake or pulse felt through the engine, worse at idle
- Rough idle that smooths out somewhat at higher RPM
- Reduced power and slightly worse fuel economy
- Check engine light on, sometimes flashing during the misfire
Likely causes
- Faulty spark plug or ignition coil on cylinder 1 — the most common single-cylinder cause
- A clogged or failing fuel injector on that cylinder
- Low compression in cylinder 1 (worn piston rings or a leaking valve)
- A damaged or disconnected spark plug wire (on wire-type ignition systems)
How to diagnose it
- Swap the coil and spark plug from cylinder 1 with another cylinder — if the misfire follows the swap, the part is confirmed bad
- Check injector function (resistance test or listen for the injector's click with a mechanic's stethoscope)
- Run a compression or leak-down test on cylinder 1 if the ignition/fuel components check out fine
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Code names are compiled from open/standardized SAE and ISO references. Explanations, symptoms, causes and fixes are original. Covers generic (P0/C0/B0/U0) codes only — manufacturer-specific codes are planned for a future update.
Frequently asked questions
Can I drive with P0301?
You can usually keep driving with P0301, but don't put it off — the underlying cause can get worse or lead to further damage the longer it goes unaddressed. Get it diagnosed as soon as you reasonably can.
How much does it cost to fix P0301?
Typical repair costs for {code} range from roughly 40 to 2500 EUR, depending on the specific cause and your car — see the fixes listed above for a breakdown.
What causes P0301?
Faulty spark plug or ignition coil on cylinder 1 — the most common single-cylinder cause A clogged or failing fuel injector on that cylinder Low compression in cylinder 1 (worn piston rings or a leaking valve)
Reviewed by Artyom SemenovAutomotive Editor · Fact-checked by Yauheni Kapliarchuk, Editor-in-Chief