P0301 Cylinder 1 Misfire
Caution
Cylinder 1 is misfiring. The cause lives in that one cylinder, so the search is short: its spark plug, coil, injector or compression. Fix it within days; if the light flashes, slow down and stop soon.
- Safe to drive?
- Only gently, and not if the light flashes
- Typical cost at a shop
- $216-$953 RepairPal national averages, parts and labor
- Emissions test
- Yes, while the check engine light is on, most OBD emissions tests fail the car.
- Carmaker bulletins
- 2 notes with links
What it means
This is the same detection as P0300, the crankshaft slowing where a power stroke should be, but it is on cylinder 1 only. A single-cylinder misfire is good news for diagnosis: everything that can cause it serves that one cylinder.
The technical version
The misfire monitor attributes misses to a cylinder from crankshaft timing. A rate high enough to damage the catalytic converter flashes the light while it happens. Where the car supports Mode 06, misfire counts for each cylinder confirm which one misses.
Official name: Cylinder 1 Misfire Detected.
Symptoms
- A shake at idle.
- A stumble when accelerating.
- A flashing check engine light if it is bad.
Causes, most likely first
| Cause | How likely | How to tell |
|---|---|---|
| A worn or fouled spark plug in cylinder 1 | most common | Plug past its interval; its look tells a lot. |
| Cylinder 1's ignition coil (or plug wire on older cars) | common | Swap the coil: the misfire moves with it. |
| A clogged or dead injector on cylinder 1 | less common | Swap the injector where easy: the misfire follows. |
| A vacuum leak at cylinder 1's intake runner | less common | Misfire mostly at idle. |
| Low compression in cylinder 1 | rare | A compression test shows it. |
How likely is our ranking from repair data and common practice, not a published rate.
What the live data shows
Per-cylinder misfire counts make this code easy to chase where the car reports them: cylinder 1 counting while the others stay near zero confirms it. Read the freeze frame: a misfire only under load points to spark (coil or plug); at idle, to a leak or the injector.
What to check first, in order
-
If the light flashes, slow down and stop soon.
The converter can overheat.
What the data shows: Counts rise fast.
Cost: free
-
Pull and look at the cylinder 1 spark plug.
Cheap and often the cause.
What the data shows: After a new plug, cylinder 1 counts should drop.
Cost: $288-$399 at a shop (Spark plug replacement, RepairPal)
-
Swap coil 1 with another cylinder.
Free test of the coil.
What the data shows: If the misfire code moves (P0301 becomes P0302 or similar), replace the coil.
Cost: $238-$320 at a shop (Ignition coil replacement, RepairPal)
-
Swap-test or check the injector.
Next most likely.
What the data shows: Counts follow the injector.
Cost: $768-$953 at a shop (Fuel injector replacement, RepairPal)
-
Compression-test cylinder 1.
If spark and fuel are fine.
What the data shows: Not a scanner step.
Cost: a shop test
Is it safe to drive?
Caution
Only gently, and not if the light flashes. Unburned fuel reaches the converter.
A steady light and a mild stumble: drive gently and fix it within days. A flashing light: unburned fuel is overheating the catalytic converter; slow down and stop as soon as it is practical. A dead cylinder also washes its wall with raw fuel, so do not drive far on it.
Stop driving and get help if
- The check engine light flashes.
- The engine shakes hard.
What it costs
| Repair | Typical cost |
|---|---|
| Engine compression testRepairPal, updated September 3, 2026 | $216-$317 |
| Ignition coil replacementRepairPal, updated September 3, 2026 | $238-$320 |
| Spark plug replacementRepairPal, updated September 3, 2026 | $288-$399 |
| Fuel injector replacementRepairPal, updated September 3, 2026 | $768-$953 |
National averages for the full job at a shop, parts and labor, from RepairPal (updated September 3, 2026). Your price depends on the car and the area. Many of the first checks on this page cost nothing with a scanner. Ignition coil and spark plugs together were CarMD's number 3 check engine repair in 2025 ($480), ignition coil alone number 5 ($256), spark plugs alone number 10 ($299). Fuel injectors were number 7, at an average of $572. CarMD averages come from a different method (repairs reported by its users), so they can sit below RepairPal's shop estimates.
Sources for the notes: CarMD 2026 Vehicle Health Index (press release, April 22, 2026).
Can I clear it? Will it come back?
After the repair, clear the code and check cylinder 1's misfire count after the next drive. It should be at or near zero.
Will it fail an emissions test?
Yes, while the check engine light is on, most OBD emissions tests fail the car.
Carmaker notes
Service bulletins and warranty extensions that name this code. Ask a dealer to check your VIN.
-
Honda 2008-2012 Accord V6 automatic
Honda bulletin 13-078 (version 11, December 2018): piston rings on some cylinders can line up and foul the spark plugs, with P0301 to P0304. Coverage is 8 years from purchase with unlimited miles, from a class action settlement.
Honda 13-078 via NHTSA static.nhtsa.gov
-
Ford 2014-2019 Fusion and 2017-2019 Escape 1.5L EcoBoost
Ford bulletin 19-2139 (November 2019): P0300 to P0304 and related codes may come from coolant getting into a cylinder. The fix is a new short block and head gasket.
Ford TSB 19-2139 via NHTSA static.nhtsa.gov
Related codes
Also related, no guide yet: P0302, P0304.
How Obie handles P0301
Obie reads the misfire counts per cylinder where your car reports them, walks you through the coil swap, and checks the counts again after the next drive. Obie is part of ScanMyCar Pro. Codes and live sensors are free.
Questions people ask
Where is cylinder 1?
It depends on the engine. Your repair manual or an engine diagram for your exact engine shows it. Do not guess: the wrong cylinder means the wrong part.
Can I drive with P0301?
Gently for a few days with a steady light. Not with a flashing light.
Is P0301 the coil or the plug?
Swap the coil to another cylinder. If the misfire moves, it is the coil. If not, check the plug next.
Sources
- RepairPal: P0301 code page repairpal.com
- RepairPal: Engine compression test (updated September 3, 2026) repairpal.com
- RepairPal: Ignition coil replacement (updated September 3, 2026) repairpal.com
- RepairPal: Spark plug replacement (updated September 3, 2026) repairpal.com
- RepairPal: Fuel injector replacement (updated September 3, 2026) repairpal.com
- CarMD 2026 Vehicle Health Index (press release, April 22, 2026) prnewswire.com
- Honda 13-078 via NHTSA static.nhtsa.gov
- Ford TSB 19-2139 via NHTSA static.nhtsa.gov
- Texas DPS emissions testing FAQ dps.texas.gov
- Arizona myazcar.com: OBD and the check engine light myazcar.com
A guide, not a diagnosis. This page describes what P0301 generally means across OBD2 cars. What is actually wrong with your car depends on its live data and its history, and any repair decision deserves a proper diagnosis, whether that is you with a scanner or a professional with a lift.
