Combustion qualitySafety screen firstReviewed July 15, 2026
P0301Cylinder 1 misfire detected
The controller attributed a qualifying misfire pattern to Cylinder 1.
Conditions that can produce P0301
These are diagnostic branches, not a ranked parts list. Prevalence and testing order depend on the exact vehicle and failure scene.
- Spark plug, coil, boot, or ignition circuit
- Injector, connector, or cylinder fuel delivery
- Compression, leakage, valve, or valvetrain problem
- Localized intake or coolant intrusion issue
- Incorrect cylinder attribution or mechanical imbalance
What to inspect next
- Stop safely for a flashing lamp, severe vibration, overheating, or fuel odor
- Compare Cylinder 1 counts with the other cylinders
- Use controlled component substitution only when safe and documented
- Confirm compression/leakage and injector control before replacing major parts
Evidence that strengthens the answer
Cylinder counters under the failure conditionIgnition waveform or verified swap resultInjector command and balance resultCompression, leak-down, or in-cylinder evidence
Verify the repair
Preserve the pre-repair record, document exactly what changed, then repeat the relevant operating condition safely. Confirm no current or pending fault returns, review permanent-code and readiness state where applicable, and state which tests or modules remained unavailable.
This page explains a commonly standardized code at a general level. Confirm the exact definition, module, status, test conditions, thresholds, wiring, and service process for the vehicle application using current official information.