Cylinder 1 misfire detected
P0301 means the controller attributed a qualifying misfire pattern to Cylinder 1. It does not identify a failed part or establish a repair price by itself.
Conditions that can produce P0301
These are diagnostic branches, not a ranked shopping list. Testing order depends 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
What strengthens the answer
Prove what changed
Preserve the pre-repair record, document exactly what changed, and repeat the relevant operating condition safely. Confirm that current or pending faults do not return, review permanent-code and readiness state where applicable, and state which tests or modules remained unavailable.
P0301 questions
What does P0301 mean?
The controller attributed a qualifying misfire pattern to Cylinder 1.
Does P0301 identify the broken part?
No. The cylinder number narrows the investigation but does not identify whether spark, fuel, compression, air distribution, wiring, or control is responsible. Confirm the exact vehicle definition and test the relevant branches before ordering a part.
Is it safe to drive with P0301?
Do not use the code alone to decide whether the vehicle is safe to drive. Stop and arrange qualified help for severe drivability, flashing warning lamps, smoke, fuel odor, overheating, braking or steering changes, electrical heat, or high-voltage damage.
How much does P0301 cost to repair?
The code alone cannot produce a defensible repair price. Cost depends on the confirmed cause, exact vehicle, parts choice, labor time, local labor rate, tax, supplies, and whether related damage is present.
What should I record before clearing P0301?
Record the reporting module, stored or pending status, freeze-frame data, readiness state, related codes, symptoms, battery voltage, and unavailable evidence. Clearing first can erase the most useful failure-scene context.
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 using current official information.
See how this page earns trust.
These links are primary-source starting points for the page's scope. They do not replace the current manufacturer procedure, wiring, specification, or service information for a specific vehicle.
Publisher
ScanWrench Editorial is the working byline for this library. Joshua Black, founder and publisher, is responsible for publication decisions, disclosures, and corrections.
A reviewed date means an editorial scope and safety check. It is not an ASE credential, OEM authorization, or vehicle-specific repair approval.
Primary sources
- SAE J2012 — Diagnostic Trouble Code DefinitionsSAE International · Standardized DTC structure, definitions, and manufacturer-controlled ranges.
- SAE on-board diagnostics standards indexSAE International · Primary standards family for regulated OBD services, identifiers, and transport context.
- OBD frequently asked questionsU.S. Environmental Protection Agency · Public explanation of regulated emissions diagnostics and the malfunction indicator light.
Revision history
- Reviewed edition: claim boundaries, safety language, internal links, and cited source scope checked.
No material correction has been recorded after this edition. If that changes, the correction and review date will be listed here.
Report a possible correction ↗