P0300 Random/Multiple Cylinder Misfire Detected

P0300 is a random or multiple-cylinder misfire code. It means the module detected misfire activity that is not limited to one clearly identified cylinder.

Code details

Generic OBD-II · P0

System: Ignition / Misfire
Code type: Generic (SAE / ISO controlled)
Standard: SAE J2012 / ISO 15031-6

Diagnostic boundary

A diagnostic trouble code reports that a monitored test failed. It does not prove one specific part is bad, and manufacturer logic can add vehicle-specific conditions.

Do not replace all ignition coils or plugs without checking whether the misfire is cylinder-specific, load-specific, fuel-related, or mechanical.

Symptoms of P0300

Rough or shaking idle that may come and go.
Stumble, jerk, or hesitation under acceleration.
A flashing check-engine light when the misfire is active.
Noticeably worse fuel economy.

Common causes of P0300

Worn spark plugs, coils, or plug wires across several cylinders.
Vacuum or intake leaks leaning out the mixture.
Weak fuel delivery — pump, filter, pressure, or dirty injectors.
Low or uneven compression, or EGR/PCV faults.

Useful checks before replacing parts

Use freeze-frame data, misfire counters, and cylinder contribution data where available.
Check ignition, fuel delivery, air leaks, compression, cam/crank correlation, and recent service work.
Diagnose active misfire quickly because prolonged misfire can overheat the catalyst.

Related OBD-II codes

These nearby ignition / misfire entries can help compare wording and pin down the fault area.