P0300 — Random/Multiple Cylinder Misfire Detected
The engine control module has detected misfires across multiple cylinders.
- Applies to
- All OBD-II vehicles (any make or model)
- Est. repair cost
- $100 – $900
- Time to fix
- 1-3 hours
What it means
P0300 is a generic powertrain code indicating the ECM detected that one or more cylinders are misfiring at random. Ignoring it can damage the catalytic converter and cause rough running.
Symptoms
- Engine runs rough or shakes at idle
- Check engine light flashing or steady
- Loss of power during acceleration
- Increased fuel consumption
How to fix it
- 1
Inspect and replace spark plugs
1 hour1. Remove ignition coils. 2. Check spark plug gap and condition. 3. Replace worn or fouled plugs with the manufacturer-specified type. 4. Clear the code and test drive.
- 2
Test ignition coils
45 minutes1. Swap a suspect coil to a different cylinder. 2. Re-scan to see if the misfire follows the coil. 3. Replace the faulty coil.
Frequently asked questions
Can I drive with a P0300 code?
Short distances may be fine, but sustained driving with active misfires can overheat and destroy the catalytic converter. Diagnose promptly.
Is P0300 expensive to fix?
It depends on the cause. Spark plugs are inexpensive; a failing fuel injector or compression issue can be much costlier.
Last updated July 13, 2026
Guidance only — always consult a qualified professional or the official service manual before carrying out repairs.