P0300
High SeverityRandom/Multiple Cylinder Misfire Detected
Ignition System
What Does P0300 Mean?
The engine is misfiring across multiple cylinders. This is often caused by something that affects all cylinders — spark plugs, fuel quality, vacuum leak, or low compression.
Common Fix
Replace spark plugs
Estimated Cost (DIY)
$20 - $500
Symptoms
- ⚠️Rough idle
- ⚠️Flashing check engine light
- ⚠️Loss of power
- ⚠️Engine shaking or vibration
Related Symptoms
Common Causes
How to Diagnose P0300
- 1Check spark plugs — replace if worn or fouled
- 2Inspect ignition coils for cracks
- 3Check for vacuum leaks
- 4Test fuel pressure
OEM Diagnostic Flowchart
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Related Resources
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OEM Manual Evidence
Browse →A L L Diagnostic Trouble Codes ( DTC ) — 2013 GMC Truck Yukon XL Denali AWD V8-6.2L Service Manual | Operation CHARM Operation CHARM : Car...
A L L Diagnostic Trouble Codes ( DTC ) — 2013 GMC Truck Yukon XL Denali 2WD V8-6.2L Service Manual | Operation CHARM Operation CHARM : Car...
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A L L Diagnostic Trouble Codes ( DTC ) — 2013 GMC Truck Yukon XL 4WD V8-5.3L Service Manual | Operation CHARM Operation CHARM : Car repair...
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Related Symptoms
Browse →Rough idle often traces back to ignition, air metering, vacuum leaks, or timing-related faults before it becomes a full misfire complaint.
A check-engine light is a graph entry point into code pages, symptom-specific diagnosis, and the exact repair categories most often associated with those failures.
Exact Vehicle Hubs
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Open the exact vehicle hub grounded by OEM manual evidence related to P0300.
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Related Codes
Cylinder 1 is misfiring — not firing properly. Could be spark plug, coil, injector, or compression issue on that specific cylinder.
Cylinder 2 is misfiring.
The engine is running lean on bank 1 — too much air or not enough fuel. The ECM has maxed out its fuel trim trying to compensate. Common causes include vacuum leaks and dirty MAF sensors.
Frequently Asked Questions
- Is P0300 serious?
- Yes — a flashing check engine light means active misfires that can damage the catalytic converter. Pull over if the light flashes.
- Can bad gas cause P0300?
- Yes — contaminated or low-octane fuel can cause random misfires. Try running a tank of premium fuel with fuel system cleaner.
Related Repair Guides
If your vehicle has triggered P0300, these DIY repair guides may help: