P0300: Random / Multiple Cylinder Misfire Detected
P0300 means the engine detected misfires on more than one cylinder. It's one of the most common check-engine codes and usually points to ignition, fuel delivery, or air-intake problems.
Severity: serious · System: Powertrain · Safe to drive: no — get it checked. Drive to a shop soon — a flashing light can damage the catalytic converter within miles.
Symptoms
- Rough idle
- Loss of power
- Flashing check engine light
- Hesitation on acceleration
Common causes
- Worn spark plugs
- Failing ignition coil
- Vacuum leak
- Bad fuel injector
- Low fuel pressure
Fair repair prices
| Spark plug replacement | $100–$250 |
|---|---|
| Ignition coil replacement | $150–$400 |
| Fuel injector replacement | $250–$900 |
| Vacuum leak repair | $100–$400 |
Ranges are US market averages (parts and labor). If your shop's quote is above the high end, ask for a line-item breakdown or run it through the invoice checker.
Other codes
- P0301 — Cylinder 1 Misfire Detected
- P0420 — Catalyst System Efficiency Below Threshold (Bank 1)
- P0430 — Catalyst System Efficiency Below Threshold (Bank 2)
- P0171 — System Too Lean (Bank 1)
- P0174 — System Too Lean (Bank 2)
- P0442 — Evaporative Emission Control System Leak (Small)
- P0455 — Evaporative Emission Control System Leak (Large)
- P0128 — Coolant Temperature Below Thermostat Regulating Temperature