P0301 code: Cylinder 1 Misfire Detected
P0301 means cylinder 1 Misfire Detected. The code says where to look, not what failed — the fix depends on which cause your car actually has.
What P0301 means
A misfire means a cylinder isn't burning its air-fuel mixture properly. Unlike P0300 (random/multiple), P0301 points to one specific cylinder — number 1 — which actually makes it easier to diagnose. The usual cause is that cylinder's spark plug or ignition coil, and a quick test is to swap the coil or plug with a neighboring cylinder and see if the misfire follows. Less commonly it's a clogged or dead fuel injector, or low compression in that cylinder from a valve or ring problem. Because unburned fuel can overheat the catalytic converter, a steady misfire shouldn't be left for long.
P0301 symptoms
- Rough idle or shaking, often felt at a stop
- Loss of power or hesitation under acceleration
- Flashing check-engine light during an active misfire
- Reduced fuel economy
- Engine may stumble or be hard to start
What it costs to fix P0301
Typical range: $80–$600 · about ~0.3–3 hrs of labor
| If the cause is… | Part | Labor |
|---|---|---|
| Spark plug (single) | $4–$30 | ~0.3–1.5 hrs |
| Ignition coil (single) | $30–$150 | ~0.3–1 hrs |
| Fuel injector (single) | $100–$400 | ~1–3 hrs |
A single plug or coil is the cheap, common fix; an injector is pricier; low compression (a valve or ring issue) is a major repair that varies too much to quote — get it diagnosed if plug, coil, and injector all check out.
The price swings on which cause it turns out to be — so confirm the cause before paying. Diagnose P0301 for my exact vehicle →
How to fix P0301
Easy — basic tools, most owners can do this
- Locate cylinder 1 on your engine
Cylinder numbering varies by manufacturer — number 1 is at the front of most inline fours, but V6/V8 layouts differ between brands. Confirm the location from a diagram for your engine first; working on the wrong cylinder wastes the whole diagnosis.
- Swap the cylinder 1 coil with a neighbor
Move coil 1 to another cylinder, clear the code, and drive. If the code changes to the other cylinder (say P0303), the coil is bad — replace it. If P0301 stays put, the coil is fine and the fault is in the plug, injector, or cylinder itself.
- Inspect and replace the cylinder 1 spark plug
With the coil out, pull plug 1 and look for a cracked insulator, worn electrodes, oil fouling, or an incorrect gap. A single plug is cheap enough that replacing it while you're in there is almost always worth it.
- Test the cylinder 1 injector
If plug and coil check out, listen to injector 1 with a mechanic's stethoscope for a steady click at idle, or swap it with a neighboring injector and see if the misfire follows. A dead or clogged injector on one hole mimics an ignition fault.
- Run a compression test on cylinder 1
With spark and fuel proven good, thread a compression gauge into hole 1 and compare the reading to the other cylinders. A noticeably low number points to a valve or ring problem — shop territory.
DIY or shop? The coil-swap test, a new plug, and even an injector swap are classic driveway jobs on most engines — coil-on-plug coils come off with one bolt, and the swap test costs nothing. It becomes shop work if compression comes back low, or if cylinder 1 on your particular engine hides under the intake manifold.
Tools for the DIY steps: OBD-II scanner · Spark plug socket · Ratchet and extension · Small socket set for the coil bolt · Compression tester (optional) · Mechanic's stethoscope (optional)
Not sure which step applies to your car? Get the likely cause for your exact vehicle before buying anything for P0301.
Start a case with P0301 and your car. Redline weighs these causes against what your car shows, and names the check that would settle it before you buy parts.
Can I drive with P0301?
Redline can’t determine from a symptom or code alone whether your car is safe to drive.
P0301 on specific vehicles
The likely causes shift by model. We’ve written up the patterns we see most:
P0301: common questions
Can I drive with P0301?
That can't be judged from a code alone. With a steady (not flashing) light, get it looked at soon. If the light is flashing, the active misfire is dumping raw fuel into the catalytic converter and can destroy it; stop driving and have the car towed.
How do I know if it's the coil or the spark plug?
The classic test is to swap cylinder 1's coil (or plug) with a neighboring cylinder and clear the code. If the misfire moves to the other cylinder, the part you moved is the culprit. It's a cheap way to avoid replacing the wrong thing.
How much does it cost to fix P0301?
Often modest — a single spark plug or coil is the common, inexpensive fix. It rises if the cause is a fuel injector, and a compression problem (valve or ring) is a major repair that varies widely. Confirm the cause before spending.
Should I replace all the coils or just cylinder 1?
If only cylinder 1 is misfiring, replacing just its coil/plug is reasonable. Some owners do all of them at once if the parts are old and high-mileage, to avoid chasing the next one — but it isn't required to fix P0301.
Symptoms that trigger P0301
Drivers who get this code often notice one of these. Each has its own causes and cost guide:
Related trouble codes
Don’t have a scanner yet? A ~$25 Bluetooth adapter reads codes like P0301 from your phone. See our guide to the best OBD2 Bluetooth adapters. Run a repair shop? See Redline for shops.
Generic OBD-II reference. Manufacturer-specific behavior varies. Confirm with a scan tool and, for safety-related codes, a professional inspection. Cost ranges are reference ranges, not quotes.
Seeing P0301 on your car?
Every problem becomes a Case. Tell Redline what the car is doing: it shows what the evidence supports, what’s still missing, and what to check next, before you approve a repair.
“Inner pad ~1 mm. Outer pad 3 mm.”
Next: check the slide pins move freely before buying parts.