P0301
Cylinder 1 Misfire Detected
Your engine's cylinder 1 is not firing properly. This means the fuel-air mixture in that cylinder is not igniting correctly, causing the engine to run rough and lose power.
- SEV
- 3/5
- DRIVE
- CAUTION
- DIY
- $20–$200
- SHOP
- $150–$600
Quick answer
AI-CITATION READYWhat it means
Can you drive with it?
Most common causes
- Worn or fouled spark plug in cylinder 1
- Faulty ignition coil on cylinder 1
- Damaged or worn spark plug wire or boot
Typical repair cost
DIY usually runs $20–$200. Typical shop repair lands around $150–$600, depending on the root cause.
01 / Definition
The PCM has detected that cylinder 1 is misfiring based on crankshaft position sensor data showing irregular rotation. The misfire rate has exceeded the manufacturer's threshold for triggering a diagnostic trouble code. This can be caused by ignition, fuel delivery, or mechanical issues specific to cylinder 1.
02 / Drive status
With caution. You can drive short distances at low speeds, but prolonged driving risks catalytic converter damage and increased emissions.
03 / Symptoms
- Rough idle or engine vibration
- Check Engine Light flashing or steady
- Loss of power during acceleration
- Engine hesitation or stumbling
- Increased fuel consumption
- Raw fuel smell from exhaust
04 / Causes
| 1 | Worn or fouled spark plug in cylinder 1 | high |
|---|---|---|
| 2 | Faulty ignition coil on cylinder 1 | high |
| 3 | Damaged or worn spark plug wire or boot | medium |
| 4 | Clogged or failing fuel injector on cylinder 1 | medium |
| 5 | Vacuum leak near cylinder 1 intake | medium |
| 6 | Low compression in cylinder 1 (worn valve or piston ring) | low |
05 / Diagnostic sequence
- 01Read freeze frame data to identify conditions when misfire occurred
- 02Inspect spark plug on cylinder 1 for wear, fouling, or damage
- 03Check ignition coil on cylinder 1; swap with another cylinder to confirm
- 04Test fuel injector on cylinder 1 for proper operation
- 05Perform a compression test on cylinder 1
- 06Check for vacuum leaks around the intake manifold near cylinder 1
06 / Repairs
| 1 | Replace spark plug on cylinder 1 | $5–$25 |
|---|---|---|
| 2 | Replace ignition coil on cylinder 1 | $30–$100 |
| 3 | Replace spark plug wire or boot if applicable | $20–$60 |
| 4 | Clean or replace fuel injector on cylinder 1 | $50–$200 |
| 5 | Repair vacuum leak if found | $20–$150 |
MFG / Manufacturer notes
These supplements add make-specific diagnostic framing. Pages without full matrix backing or lane approval stay guarded and canonicalize back here until they are explicitly approved for indexing.
- Open
Audi P0301
Approved indexable child page
07 / Related codes
08 / FAQ
Can a misfire damage my catalytic converter?
Yes. Unburned fuel from a misfiring cylinder enters the exhaust and can overheat and damage the catalytic converter if not addressed promptly.
Why is only cylinder 1 misfiring?
Single-cylinder misfires usually point to a component specific to that cylinder, such as its spark plug, ignition coil, or fuel injector.
How do I find cylinder 1 on my engine?
Cylinder numbering varies by manufacturer and engine layout. Consult your vehicle's repair manual for the correct cylinder identification.
09 / Source and method
- DATA BASIS
- OBD-II REFERENCE + OBD2.HELP
- METHOD
- STATIC VALIDATION
- SAFETY
- INFORMATIONAL
This page combines OBD-II diagnostic reference data with OBD2.help generated diagnostic guidance for code meaning, likely causes, and repair direction.
Publishing uses deterministic schema and build validation, plus manual spot checks on representative pages before release.
Safety-critical diagnosis and repairs should be confirmed with a qualified mechanic, especially when the vehicle is misfiring, overheating, or losing power.