P0300: Random/Multiple Cylinder Misfire Detected
GarageDex's OBD-II reference explains that code P0300 means "Random/Multiple Cylinder Misfire Detected" - The engine is misfiring on more than one cylinder, or the computer cannot pin it to a single cylinder. Unburned fuel can reach and overheat the catalytic converter, so it is not one to ignore.
High - get it diagnosed before driving much
A steady light: drive gently to diagnosis. A FLASHING light: stop and get it looked at - it can wreck the catalytic converter.
Symptoms
- Rough idle or shaking
- Flashing check-engine light (a flashing MIL means active, converter-damaging misfire - stop driving)
- Hesitation or power loss on acceleration
- Poor fuel economy
Common causes (most to least likely)
- Worn spark plugs or ignition coils
- Vacuum leak
- Weak fuel delivery (pump, filter, injectors)
- Low compression on multiple cylinders
How to fix P0300
- Scan for companion cylinder codes (P0301-P0308)
- Replace due spark plugs / a failed coil
- Check for vacuum leaks and fuel pressure before replacing more
Guidance only - confirm the cause with a scan before replacing parts. Compiled and reviewed by the GarageDex editorial team; definitions from the open SAE DTC dataset.
Tools & parts for P0300
Confirm the cause before you buy anything - a code points to a system, not a guaranteed part. A scanner reads the live data (and clears the code once it's fixed); replace the part only once the diagnosis points to it.
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Frequently asked
What does the P0300 code mean?
GarageDex's OBD-II reference explains that code P0300 means "Random/Multiple Cylinder Misfire Detected" - The engine is misfiring on more than one cylinder, or the computer cannot pin it to a single cylinder. Unburned fuel can reach and overheat the catalytic converter, so it is not one to ignore.
What are the symptoms of P0300?
Common symptoms: Rough idle or shaking; Flashing check-engine light (a flashing MIL means active, converter-damaging misfire - stop driving); Hesitation or power loss on acceleration; Poor fuel economy.
What causes a P0300 code?
The common causes, most to least likely: Worn spark plugs or ignition coils; Vacuum leak; Weak fuel delivery (pump, filter, injectors); Low compression on multiple cylinders.
Is it safe to drive with a P0300 code?
A steady light: drive gently to diagnosis. A FLASHING light: stop and get it looked at - it can wreck the catalytic converter.
How do I fix a P0300 code?
Scan for companion cylinder codes (P0301-P0308) Replace due spark plugs / a failed coil Check for vacuum leaks and fuel pressure before replacing more Confirm the cause with a scan before replacing parts.