P0300
PowertrainIgnition Misfirecritical severityRandom/Multiple Cylinder Misfire Detected
What P0300 Means
The PCM has detected misfires occurring in multiple cylinders randomly. This is different from a single-cylinder misfire and often points to a system-wide issue.
Symptoms
- Check Engine Light (flashing if severe)
- Rough idle
- Vibration
- Loss of power
- Hesitation
- Poor fuel economy
- Possible catalyst damage
Common Causes
- Vacuum leak
- Low fuel pressure
- Faulty spark plugs (all)
- Ignition coil pack failure
- EGR valve stuck open
- Low compression (multiple cylinders)
- Wiring harness issue
- MAF sensor problem
Diagnostic Steps
- Check for vacuum leaks (smoke test)
- Test fuel pressure
- Inspect spark plugs
- Test ignition coils
- Check fuel injectors
- Test compression
- Check MAF sensor
- Monitor fuel trim values
Where to start: Start with spark plugs and vacuum leaks. Flashing CEL means severe misfire - stop driving to protect catalytic converter.
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