P0301
High SeverityCylinder 1 Misfire Detected
Ignition System
What Does P0301 Mean?
Cylinder 1 is misfiring — not firing properly. Could be spark plug, coil, injector, or compression issue on that specific cylinder.
Common Fix
Replace spark plug or ignition coil on cylinder 1
Estimated Cost (DIY)
$20 - $500
Symptoms
- ⚠️Rough idle
- ⚠️Loss of power
- ⚠️Check engine light (may flash)
- ⚠️Vibration
Related Symptoms
Common Causes
How to Diagnose P0301
- 1Swap spark plug with known good cylinder — see if misfire moves
- 2Swap coil with another cylinder — see if code follows
- 3Check injector operation
- 4Run compression test if spark and fuel are good
OEM Diagnostic Flowchart
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Related Resources
Repair guides, symptom pages, and wiring diagrams related to P0301.
OEM Manual Evidence
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Exact Repair Workflows
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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 P0301.
Open the exact vehicle hub grounded by OEM manual evidence related to P0301.
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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 2 is misfiring.
The fuel injector on cylinder 1 has a circuit fault. It may not be firing.
Frequently Asked Questions
- How do I find cylinder 1?
- Cylinder 1 location varies by engine. Check your repair manual. On most inline engines, it is at the front (belt end).
- Can I just replace one spark plug?
- You can, but it is recommended to replace all plugs at the same time since they wear together.
Related Repair Guides
If your vehicle has triggered P0301, these DIY repair guides may help: