Misfire · Fault code

P0301

Cylinder 1 Misfire

The ECU attributed misfires specifically to cylinder 1. Because it names a cylinder, one swap test splits ignition from everything mechanical.

Severity EXPERT Moderate — diagnose before it gets worse

Driveability EXPERT Drive with caution — the ECU is already protecting itself

Tuning EXPERT Diagnose first — do not tune onto this

Check first — in this order

The order is the product. A list of "possible causes" is what every parts site publishes, and it is why people replace parts blindly.

Swap the coil (and plug) with an adjacent cylinder and clear. If the misfire follows the coil, it is ignition; if it stays on cylinder 1, it is not. This one test is worth more than any parts list. EXPERT
If it stays, test that cylinder mechanically — compression and leak-down. EXPERT
Check the injector on that cylinder, electrically and for flow, before condemning mechanicals. EXPERT

What this code does not license you to replace

That cylinder-1 hardware has failed before the swap test has moved or not moved the misfire.
That it is always ignition. The swap test exists precisely because it is not.

Companion codes

Codes whose presence alongside P0301 changes the path.

P0300 P0171

No workshop sign-off yet. The diagnostic order on this page has had a technical review of the knowledge model, performed by a model — not a manufacturer certification and not a mechanical inspection of any vehicle. No tuner has yet put their name to this ordering. Treat it as a reasoned starting point, confirm with measurement, and get a professional to sign off before you condemn a part.

Built by DMS Tuned

Stuck on P0301? Send us the log.

DMS Tuned is a real ECU-tuning shop. If you have a boost/requested-vs-actual log, run it through the analyser first — then message us and we will read it with you before you spend money on parts.

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