Diagnostic code
P0301 Code: Cylinder 1 Misfire Detected
P0301 means cylinder 1 is not burning its air-fuel mixture consistently. The problem may be isolated to that cylinder, such as a spark plug, coil, injector, compression issue, or local air leak near the intake runner.
Can I drive?
Avoid driving if the light flashes or the engine shakes. If symptoms are mild, drive only as needed to get the vehicle inspected.
Repair range
$100-$1,400
Scanner note
Basic OBD-II scanner with live data
Plain-English Meaning
P0301 means cylinder 1 is not burning its air-fuel mixture consistently. The problem may be isolated to that cylinder, such as a spark plug, coil, injector, compression issue, or local air leak near the intake runner.
Common Causes
Symptoms
- Engine shake at idle
- Flashing check engine light
- Poor acceleration
- Fuel smell from exhaust
Diagnostic Steps
- 1Confirm cylinder numbering for the engine
- 2Swap coil or plug with another cylinder when appropriate
- 3Inspect injector operation and connector fit
- 4Check for local vacuum leaks
- 5Run compression testing if the misfire stays on cylinder 1
Confusable And Related Codes
P0300
Compare →P0300 means the engine is misfiring randomly or across multiple cylinders instead of one clearly identified cylinder. Ignition, fuel, air leaks, compression problems, or timing issues can all interrupt combustion and trigger this code.
P0302
Compare →P0302 means cylinder 2 is misfiring enough for the engine computer to identify it. The cause may be electrical, fuel-related, mechanical, or an air leak that affects that cylinder more than the others.
P0303
Compare →P0303 means cylinder 3 has a repeat misfire pattern. A technician will usually confirm the cylinder location, inspect ignition parts, check injector behavior, and rule out compression or valve problems before replacing parts.
P0304
Compare →P0304 means cylinder 4 is not firing reliably. The code narrows the search to one cylinder, but the final cause still has to be separated between spark, fuel, air, compression, and wiring faults.
FAQ
What cylinder is P0301?
P0301 points to cylinder 1, but cylinder numbering depends on the engine layout.
Can I replace only one spark plug?
You can for diagnosis, but plugs are often replaced as a set when they are worn.
Why did P0301 move after swapping coils?
If the misfire follows the coil, the coil is likely part of the fault.
This page is educational and is not a substitute for hands-on vehicle diagnosis. Source notes: Code meaning verified against OBD-II reference sources; explanation is original.