All codes
P0301Engine Problems
Cylinder 1 Misfire Detected - Diagnosis Guide
Complete guide to P0301 cylinder 1 misfire. Find out what's causing the misfire and how to fix it step by step.
What you may notice
Symptoms
- 01Check engine light on or flashing
- 02Rough idle with engine shake
- 03Loss of power
- 04Increased fuel consumption
- 05Possible backfire
Where to look first
Common causes
- 01Worn spark plug in cylinder 1
- 02Faulty ignition coil
- 03Damaged spark plug wire (older vehicles)
- 04Fuel injector problem
- 05Compression loss in cylinder 1
A sensible sequence
Best diagnostic order
- 01Confirm cylinder 1 and review freeze-frame conditions.
- 02Swap the coil or plug and see whether the misfire follows.
- 03If it stays, test the injector, vacuum leaks, and compression.
Step by step
What to check and repair
- 01Replace cylinder 1 spark plug
- 02Swap coil to test, replace if faulty
- 03Test fuel injector operation
- 04Check compression
- 05Inspect valve train if compression is low
What Does P0301 Mean?
The P0301 code means that cylinder 1 is experiencing a misfire. The engine control module monitors crankshaft speed and detects when a cylinder is not contributing its share of power.
Cylinder 1 Location
Cylinder 1 is typically at the front of the engine in inline configurations, or follows a specific firing order pattern in V-type engines. Consult your vehicle's service manual for exact location.
Quick Diagnosis Tip
A simple way to test if it's ignition-related: swap the ignition coil from cylinder 1 with another cylinder. If the misfire follows the coil, you've found your problem.