Parts
$15–150
P0301 — Cylinder 1 Misfire Detected
STOPIs it safe to drive? One cylinder is misfiring. Light driving may be okay, but a flashing light means it's damaging the catalytic converter — don't push it.
What P0301 means
Cylinder 1 specifically is failing to fire cleanly. Because it's isolated to one cylinder, the cause is usually that cylinder's plug, coil, or injector — easy to chase by swapping parts between cylinders.
Most likely causes (in order)
- Spark plug or coil on cylinder 1
- Fuel injector for cylinder 1 (clogged or dead)
- Low compression on that cylinder (valve/ring)
- Vacuum leak local to that runner
Symptoms you might notice
- Rough idle / vibration
- Power loss
- Smell of unburned fuel
What to check first
Swap cylinder 1's coil with cylinder 2 — if the misfire moves to P0302, you found a bad coil. Same trick with plugs and injectors. Compression-test last if spark and fuel are good.
Repair cost & difficulty
Labor
0.5–2 hr
Difficulty
DIY-friendly