Cylinder 1 Misfire Detected
Powertrain · Ignition System
Cylinder 1 is not firing properly. Unlike P0300 (random misfires), this code is isolated to a single cylinder, making diagnosis more straightforward.
- Faulty spark plug in cylinder 1Most common
- Bad ignition coil on cylinder 1Most common
- Clogged fuel injector on cylinder 1Common
- Low compression in cylinder 1Less common
Vehicles most commonly affected by P0301
Cylinder 1 misfire codes are disproportionately common on Honda Civic (1.8L and 2.0L), Toyota Corolla, and Ford Fusion 2.5L — all inline-4 engines where cylinder 1 is at the front of the engine and most exposed to heat cycles. Also common on BMW 3 Series N52/N54 engines where coil failures affect specific cylinders.
Real-world P0301 diagnosis scenario
A 2012 Honda Civic with 72,000 miles stores P0301 and P0300 together after a rough cold start. The driver notices a vibration at idle that smooths out after 5 minutes of warming up. Classic symptom of a failing coil-on-plug ignition coil that fails when cold but partially recovers with heat. Swapping the cylinder 1 coil to cylinder 3 and resetting the codes confirms the diagnosis — P0303 now appears instead of P0301. One coil replacement ($65–$120) resolves the issue completely.
The swap test is the fastest way to confirm a bad coil for P0301. Move the cylinder 1 coil to cylinder 3. If the misfire code changes to P0303, the coil is bad. If P0301 persists, the problem is the injector, spark plug, or compression — not the coil.
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Frequently asked questions about P0301
What does P0301 mean?
Cylinder 1 is not firing properly. Unlike P0300 (random misfires), this code is isolated to a single cylinder, making diagnosis more straightforward.
Is P0301 serious?
Drive cautiously — prolonged misfire damages catalytic converter.
How much does it cost to fix P0301?
Repair costs for P0301 range from $30 – $100 depending on the root cause and your vehicle.
Can I drive with P0301?
No — this code indicates a serious issue. Stop driving and have the vehicle inspected immediately.
Should I replace all coils when one fails?
On vehicles over 80,000 miles, replacing all coils at once when one fails is cost-effective — the remaining coils are likely to fail within 20,000–30,000 miles anyway. The part cost is roughly the same; most of the expense is labor, which doesn't increase proportionally when doing all at once.
Can a bad spark plug cause only P0301?
Yes. A single fouled, cracked, or worn spark plug in cylinder 1 will cause P0301 without triggering other cylinder codes. This is why spark plugs should always be inspected before replacing the coil.
Will P0301 damage my engine if I keep driving?
A steady P0301 (not flashing) means the misfire is intermittent and not continuously dumping raw fuel into the catalytic converter. Drive cautiously to a shop within 1–2 days. A flashing check engine light with P0301 means stop driving immediately.