Trouble code P0300
P0300: random or multiple cylinder misfire.
P0300 is the generic OBD-II code “Random/Multiple Cylinder Misfire Detected”. P0301 to P0308 each name a single cylinder.
Flashing light? Stop driving.
A flashing check engine light means stop driving, to avoid damaging the catalytic converter. Have the car checked by a professional.
What each part of the code means
- P
- Powertrain
- 0
- Generic code, defined by SAE
- 3
- Ignition system or misfire
- 00
- The specific fault
P0300 and the single-cylinder codes
- P0300
- Random/Multiple Cylinder Misfire Detected
- P0301
- Cylinder 1 Misfire Detected
- P0302
- Cylinder 2 Misfire Detected
- P0303
- Cylinder 3 Misfire Detected
- P0304
- Cylinder 4 Misfire Detected
- P0305
- Cylinder 5 Misfire Detected
- P0306
- Cylinder 6 Misfire Detected
- P0307
- Cylinder 7 Misfire Detected
- P0308
- Cylinder 8 Misfire Detected
How serious is it?
DeepDiag rates a stored P0300 or P0301 to P0308 as major, and a pending one as pending. The rating is a starting point, not a safety check.
Possible causes
California's OBD rules define a misfire as a cylinder that doesn't burn its fuel, whether from a missing spark, poor fuel metering or poor compression. The engine computer spots a misfire as a brief change in crankshaft speed.
In no particular order: which one is likeliest depends on your car and its data.
- Ignition: worn or fouled spark plugs, failing coils or worn plug wires. If your car doesn't report misfire counts for each cylinder, move a coil or plug to another cylinder and see whether the misfire follows it.
- Air leaks: cracked vacuum hoses or failed intake gaskets that let in air the engine computer doesn't measure.
- Fuel delivery: low fuel pressure, from a failing pump or a blocked filter, or injectors that are clogged or faulty.
- Sensors: a faulty crankshaft, camshaft or MAF sensor.
- EGR: a faulty exhaust gas recirculation (EGR) system.
- Mechanical problems: low compression, worn or damaged valves, a failed head gasket, or a slipped or stretched timing belt or chain. A compression test at a shop can rule these in or out.
- Engine software: some makers have released updates that address misfire codes. Search NHTSA's recalls page by year, make and model for a service bulletin.
What to check in the data
- Misfire monitor tests: a general result, plus a result for each cylinder up to cylinder 12, where the car reports them.
- Emissions readiness: whether the misfire monitor has completed its self-test since codes were last cleared.
- Freeze frame: the sensor snapshot from the moment the fault was recorded.
- A recorded drive: live sensor data that you can record on a drive for the AI to review, including a guided test drive.
- Other codes: a failure in one component can set a code in another, so read every stored and pending code.
Before you clear it or buy parts
Clearing erases stored and pending codes and resets the emissions readiness checks, so the car may fail an emissions test until it has been driven enough for them to complete again. If a stored code comes straight back, that points to an active fault.
Rank the possible causes by likelihood, then run the simplest, cheapest test that would confirm the cause before you buy a part. Read what to do before you clear codes.
How DeepDiag helps
DeepDiag reads P0300 and the data above, then explains in plain language what the data shows, what the AI suspects and how confident it is. It also suggests checks to run before you buy parts, and says whether it's a job you can do yourself.
DeepDiag gives an AI-assisted reading of the data your car reports. It isn't a professional inspection, a safety check or a guarantee, and the AI can be wrong. Every feature needs an active Premium subscription.
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Related
Sources
The possible causes, definitions and repair tips on this page come from these sources, checked in November 2026. What DeepDiag reads and how it rates a code come from the app itself.