P0300 - Random/Multiple Cylinder Misfire Detected
P0300 is a generic powertrain diagnostic trouble code indicating Random/Multiple Cylinder Misfire Detected. It relates to the Ignition System / Misfire system.
DTC Breakdown (SAE J2012)
| System | Powertrain (P) |
| Type | Generic |
| Subsystem | Ignition System / Misfire |
| Fault Index | 00 |
| Standard | SAE J2012 / ISO 15031-6 |
What does diagnostic code P0300 mean?
The powertrain control module has detected random or multiple cylinder misfires, meaning the combustion process is failing in multiple cylinders without a single consistent pattern. The crankshaft sensor detected sudden speed drops.
Severity Level & Driveability Details
Severity: High
Misfiring cylinders dump unburned fuel into the exhaust, which can melt the catalytic converter in minutes. A flashing check engine light indicates an active catalyst-damaging misfire.
Common Symptoms of P0300
- Check engine light flashing continuously.
- Rough idle, engine shaking, or shuddering.
- Severe loss of engine power, especially under acceleration.
- Engine hesitation or bogging down.
- Tailpipe emissions failure.
Typical Causes for P0300
- Worn, fouled, or incorrectly gapped spark plugs.
- Failing ignition coils or deteriorated spark plug wires.
- Engine vacuum leaks letting unmetered air enter the intake.
- Low fuel pressure from a failing fuel pump or clogged fuel filter.
- egr-valve/">EGR valve stuck open or leaking exhaust gases into the intake manifold.
Diagnostic and Troubleshooting Steps
Scan for misfire counters per cylinder. Test fuel pressure with a gauge. Inspect the condition of spark plugs. Conduct a smoke test to look for vacuum leaks.
Typical Repairs and Fixes
- Replacing worn spark plugs and ignition coils.
- Repairing intake vacuum leaks.
- Replacing a failing fuel pump or clogged fuel filter.
- Cleaning or replacing the EGR valve.
Sensor Location & Parts Involved
The ignition coil and spark plug for multiple cylinders are located on top of the cylinder head on the engine block.
Clearing Code & Recurrence
Resolve the underlying ignition or fuel fault in multiple cylinders, then reset the codes using an OBD2 scanner.
Emissions & Smog Inspection Impact
Misfiring in multiple cylinders releases unburned hydrocarbons into the exhaust stream, potentially damaging the catalytic converter and raising emissions.
Free Check Engine Code Cheat Sheet (PDF)
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Related Diagnostic Codes
Sources & References
This diagnostic guide is compiled and verified against the following authority sources:
- NHTSA Recall Database
- EPA OBD II Regulations
Frequently Asked Questions about P0300
What does the random multiple cylinder misfire code P0300 mean?
The engine control module logged P0300 after detecting a combustion misfire in multiple cylinders. This indicates that the fuel-air mixture is failing to ignite properly inside the cylinder multiple chamber.
Is it safe to drive with the random multiple cylinder misfire code P0300 active?
No, driving with active misfires in multiple cylinders can ruin the catalytic converter.
How much does it cost to repair a random multiple cylinder misfire code P0300 fault?
Replacing an ignition coil or spark plug for multiple cylinders typically costs $100-$300. Replacing the fuel injector for multiple cylinders costs $200-$450.
What are the common causes of the random multiple cylinder misfire code P0300?
Trigger conditions for the random multiple cylinder misfire code P0300 include: A worn or fouled spark plug in multiple cylinders., Failed ignition coil or damaged spark plug wire for multiple cylinders., Faulty fuel injector or poor fuel atomization in multiple cylinders..
Can I clear the check engine light for random multiple cylinder misfire code P0300?
Resolve the underlying ignition or fuel fault in multiple cylinders, then reset the codes using an OBD2 scanner.
Will the random multiple cylinder misfire code P0300 cause an inspection failure?
Misfiring in multiple cylinders releases unburned hydrocarbons into the exhaust stream, potentially damaging the catalytic converter and raising emissions.