P0301: Cylinder 1 Misfire Detected

Cylinder 1 is not firing consistently. The light often comes on after a stumble, rough idle, or a flash under load.

Educational OBD2 information. Confirm on your vehicle with a scan tool. MotorBit can read this code, freeze frame, and live data over an ELM327 adapter.

What P0301 means

P0301 is a cylinder-specific misfire. The PCM counted enough incomplete combustion events on cylinder 1 to store a fault.

Why the check engine light comes on

The light turns on to warn that cylinder 1 is wasting fuel and can overheat the catalyst. A flashing light means the misfire rate is high right now.

Common causes

• Spark plug in cylinder 1 worn or gapped incorrectly
• Ignition coil on cylinder 1 failed
• Injector on cylinder 1 clogged or electrically open
• Compression loss (valve, ring, or head gasket)
• Wiring or connector issue at the coil/injector

Typical symptoms

• Rough idle
• Engine shake at stop lights
• Hesitation on takeoff
• Possible ticking or popping from the exhaust

What to do next

1. Read freeze frame to see if it happened at idle or under load.
2. Swap the coil from cylinder 1 to another cylinder and rescan. If the misfire follows the coil, replace the coil.
3. Inspect the plug and the injector connector.
4. Use MotorBit live data to watch misfire counts and fuel trims while you test.

How MotorBit helps

Open MotorBit, connect your ELM327, and read P0301 with freeze frame (RPM, load, temperature, speed at the moment the fault set). Then watch live PIDs and fuel trims instead of replacing parts by guesswork. When the repair is verified, clear the code and re-check monitors.

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