P0304
High SeverityCylinder 4 Misfire Detected
Ignition System
What Does P0304 Mean?
Cylinder 4 is misfiring.
Common Fix
Replace spark plug or coil
Estimated Cost (DIY)
$20 - $500
Common Causes
How to Diagnose P0304
- 1Swap plug/coil to test
- 2Check injector
- 3Compression test
OEM Diagnostic Flowchart
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Related Resources
Repair guides, symptom pages, and wiring diagrams related to P0304.
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...
A L L Diagnostic Trouble Codes ( DTC ) — 2013 GMC Truck Yukon XL 4WD V8-6.0L Service Manual | Operation CHARM Operation CHARM : Car repair...
A L L Diagnostic Trouble Codes ( DTC ) — 2013 GMC Truck Yukon XL 4WD V8-5.3L Service Manual | Operation CHARM Operation CHARM : Car repair...
Exact Repair Workflows
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Open the exact repair flow most commonly associated with P0304 on this vehicle.
Open the exact repair flow most commonly associated with P0304 on this vehicle.
Open the exact repair flow most commonly associated with P0304 on this vehicle.
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 P0304.
Open the exact vehicle hub grounded by OEM manual evidence related to P0304.
Open the exact vehicle hub grounded by OEM manual evidence related to P0304.
Related Codes
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.
Cylinder 3 is misfiring.
Cylinder 5 is misfiring. Only on 5+ cylinder engines.
Frequently Asked Questions
- Can a vacuum leak cause a single cylinder misfire?
- If the leak is near one intake runner, yes. But usually vacuum leaks cause P0300 (random/multiple).
- What if new plugs and coils do not fix it?
- Check fuel injector operation and run a compression test. Low compression means valve or head gasket issue.
Related Repair Guides
If your vehicle has triggered P0304, these DIY repair guides may help: