Random or multiple-cylinder misfire detected
P0300 means the controller detected crankshaft-speed variations consistent with misfire across multiple or non-fixed cylinders. It does not identify a failed part or establish a repair price by itself.
Conditions that can produce P0300
These are diagnostic branches, not a ranked shopping list. Testing order depends on the exact vehicle and failure scene.
- Ignition energy or plug problem
- Fuel quality, pressure, or injector issue
- Air leak or EGR distribution problem
- Compression, valve timing, or internal mechanical fault
- Voltage, ground, sensor, or calibration issue
What to inspect next
- Reduce load and stop safely if the lamp flashes or the engine shakes severely
- Preserve cylinder counters and freeze-frame conditions
- Determine whether the pattern is bank, cylinder, load, temperature, or fuel related
- Use controlled ignition, injector, compression, and leakage tests
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.
P0300 questions
What does P0300 mean?
The controller detected crankshaft-speed variations consistent with misfire across multiple or non-fixed cylinders.
Does P0300 identify the broken part?
No. Active severe misfire can overheat the catalyst and can create unsafe drivability. The cause may involve ignition, fuel, air, compression, timing, contamination, electrical supply, or incorrect misfire attribution. Confirm the exact vehicle definition and test the relevant branches before ordering a part.
Is it safe to drive with P0300?
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 P0300 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 P0300?
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.
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