What P0301–P0306 means
These six codes are the same fault pointing at different cylinders: P0301 is cylinder 1 misfiring, P0302 cylinder 2, through P0306 for cylinder 6. The computer has caught one specific cylinder repeatedly failing to fire — which is diagnostic gold, because it names exactly where to look.
What you’ll notice
- Rhythmic shaking — the engine limping on one leg, worst at idle
- Power loss and worse economy
- Check engine light, flashing when the misfire is active and severe
- Possible fuel smell
Likely causes and repair cost
Broad US independent-shop bands, parts and labour.
Can you drive with P0301–P0306?
Flashing light: stop — raw fuel from the dead cylinder is burning inside the catalytic converter. Steady light: gentle, minimal driving to diagnosis. Either way, this is a this-week code, not a someday code.
The misdiagnosis to avoid
Replacing parts without the free swap test. Move the suspect cylinder's coil to a neighbour: if the misfire code follows the coil (P0302 becomes P0304), the coil is convicted for zero parts cost. If it stays, the coil is innocent and the plug or injector is next. Ten minutes that prevents hundreds in guessed parts.
Describe what it’s doing in your own words and the symptom checker gives you a safe-to-drive verdict, ranked causes with costs, and notes to take to the shop — free, no sign-up.
Read the code yourself
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Check price on AmazonQuestions people ask
How do I know which cylinder is which?
The numbering is set by the manufacturer and printed in service data — cylinder 1's position varies between makes (front of engine, driver's side, passenger's side). Don't guess from the code alone: look up your specific engine's cylinder layout, or the swap test lands on the wrong cylinder.
The misfire moved cylinders after I swapped the coil. What now?
That's the test working: the fault travelled with the part, so the coil is your answer. Replace it — and given one coil failed, ask how old the plugs are; a coil often fails from working overtime against a worn plug's wider gap.
Can a misfire code mean something serious like engine damage?
It can — if coil, plug, and injector for that cylinder check out, the remaining suspect is compression: a burned valve, a broken ring, a failing head gasket at that cylinder. That's why the sequence is cheap tests first, compression test before despair, and no engine-replacement conversations until a leak-down test says where the loss is.