P0301 — Cylinder 1 misfire detected
Cylinder 1 isn’t firing consistently. The fix is usually on that cylinder’s spark, injector, or compression — not a whole-engine parts list.
What it means in plain English
P0301 flags a misfire on cylinder 1 specifically. Common path: spark plug → coil-on-plug → injector → mechanical. Swapping the coil to another cylinder (when safe and documented) is a classic shop test; if the misfire code moves, the coil is implicated. This page is for the cylinder-specific pattern; for random misfires see P0300.
Common causes
- Failed spark plug or ignition coil on cylinder 1
- Injector issue on cylinder 1
- Wiring/connector problem at that coil or injector
- Low compression / valve issue on that cylinder (less common)
What you can safely check
- Confirm it’s P0301 alone vs P0300 + P0301 together.
- If flashing: reduce load and get help — same cat-damage risk as other misfires.
- Don’t spray “guaranteed fix” additives as a diagnosis.
Pull the code yourself (disclosed)
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A reusable Bluetooth OBD-II scanner lets you read the code and freeze-frame data before authorizing “mystery” diagnostics. One option: BlueDriver Bluetooth Pro OBD-II scan tool (BlueDriver/Levanta affiliate). Any capable OBD-II reader is fine — this is not required to use Fair Auto Shops.
When to go to a shop
Persistent single-cylinder misfire needs scoped diagnosis. Ask the shop which cylinder tests they ran before authorizing injectors or head work.
Typical related repair costs (U.S. national averages)
These are related repairs shops may find after diagnosis — not a guaranteed bill for every P0301. Ranges exclude taxes, fees, diagnostics, and your location.
- $288–$399 national average for spark plug replacement (RepairPal; estimates last updated September 3, 2026; excludes taxes/fees and location; source). Labor $184–$270; parts $104–$129.
- $238–$320 national average for ignition coil replacement (RepairPal; estimates last updated September 3, 2026; excludes taxes/fees and location; source). Labor $74–$109; parts $164–$211.
Single-coil replacement is often in the ignition-coil range; a full plug set may still be recommended if plugs are due.
Related cost guides: Spark Plugs · Ignition Coil
Questions to ask before you authorize work
Use questions before you authorize a repair and how to read a repair estimate. Watch for patterns in spotting upselling.
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FAQ
Should I replace all coils if I have P0301?
Not automatically. Test or swap to confirm the failed coil. Replacing every coil “while you’re in there” can be reasonable maintenance on high-mileage cars — but it should be explained, not forced.
More check-engine codes
P0420 · P0430 · P0300 · P0171 · P0174 · P0455 · P0456 · P0442 · P0446 · P0128 · P0401 · P0133 · P0113 · P0506 · P0507 · P0700 · P0741 · P0011 · P0325 · P0340 · P0335 · P0101 · P0299 · P0135 · P0440 · P0441 · P0010 · P0500 · P0121
Hub: How to read a check-engine code · Repair cost guides · Affiliate disclosure