P0301 — Cylinder 1 Misfire Detected
High severityWhat it means
The engine control unit has counted repeated misfires in cylinder 1 specifically. Because the fault is isolated to one cylinder, the cause is usually a component that serves only that cylinder, such as its spark plug, coil or injector.
Common symptoms
- Rough idle, especially at a stop
- Engine vibration and power loss
- Flashing or steady check engine light
- Fuel smell from the exhaust in severe cases
Likely causes
- Worn or fouled spark plug in cylinder 1
- Failing ignition coil on cylinder 1
- Clogged or leaking fuel injector
- Low compression (valves, rings, head gasket)
- Wiring or connector fault at the coil
What to check first
- Swap the cylinder 1 coil with another cylinder and see if the code follows
- Inspect and replace the spark plug if worn
- Compare injector behaviour across cylinders
- Run a compression test if the misfire persists
Can you keep driving?
Like all misfires, this can overheat the catalytic converter. Keep driving to a minimum until the cause is found, and stop driving if the check engine light flashes.
Scan, log and diagnose with MechanicAI
Plug a Bluetooth OBD2 adapter into your car and let MechanicAI turn raw data into answers:
- Scan, read and clear fault codes in seconds
- Inspect every sensor with live data
- Create instant logs and automatic trip records
- And above all — analyze it all with AI for the most likely cause and clear next steps.
Related codes
All information, explanations and guidance on this page are general preliminary information only. They are estimates and may be entirely wrong, incomplete or inaccurate, or may not apply to your vehicle at all. Never take any action based on this content alone — do not decide to keep driving, clear codes, replace parts, repair or otherwise work on your vehicle based only on what you read here. In every case, and for any final decision, you must consult qualified technical personnel (a professional mechanic, an authorized service centre or an engineer) and obtain their approval before acting. MechanicAI accepts no liability or responsibility whatsoever for any damage, fault, injury, loss or outcome that may arise — directly or indirectly — from using or relying on this information, for any reason and under any circumstances. By using this page you acknowledge and accept these terms.