P0300 means Random/Multiple Cylinder Misfire Detected. The computer has counted misfires that are random or spread across more than one cylinder, rather than in a single cylinder. It is a generic OBD-II code, so the definition is the same on any make, but the most likely cause varies by engine; confirm with a scan tool and the service information for your vehicle before buying parts.
What P0300 means
The engine computer detects misfires by watching small changes in crankshaft speed: each cylinder that fires speeds the crankshaft up slightly, and one that does not leaves a gap. P0300 means misfires are random or spread over several cylinders, while P0301 to P0308 name a specific cylinder. A flashing check engine light means the misfire is severe enough to overheat the catalytic converter.
P0300 symptoms
- Rough idle, shaking or stumbling
- Loss of power and hesitation
- Flashing check engine light under load
- Higher fuel consumption
Common causes of P0300
- Something every cylinder shares: a vacuum leak, low fuel pressure, a dirty MAF sensor or contaminated fuel
- Worn spark plugs across the engine, or failing coils
- Lean codes P0171 or P0174 alongside it
- Crankshaft or camshaft timing problems
- Low compression on more than one cylinder
How to diagnose P0300
- Look at the misfire counters on a scan tool to see which cylinders are misfiring and when
- Check for other codes, especially lean, timing and sensor codes, and fix those first
- Inspect spark plugs and coils
- Check fuel pressure and look for vacuum leaks
- Run a compression test if misfires persist
Can you drive with P0300?
Only gently and briefly. If the check engine light is flashing, ease off and stop soon, because unburned fuel can overheat and damage the catalytic converter.
P0300 tips
Fix lean, timing and sensor codes first, since random misfires are often a symptom of them. Misfires that happen only under heavy load point toward ignition (plugs and coils); misfires at idle point toward vacuum leaks and fuel delivery.
Will P0300 clear itself?
If the fault stops, the computer turns off the check engine light by itself after several drive cycles without seeing it again, and the code stays in memory as history for a while. Clearing P0300 with a scan tool after a repair is fine, but if the cause is still there the code returns, sometimes within one drive. Disconnecting the battery also clears codes on most vehicles, but it erases learned fuel trims and idle settings as well.
Related codes
| Code | Meaning |
|---|---|
| P0301 | Cylinder 1 Misfire Detected |
| P0302 | Cylinder 2 Misfire Detected |
| P0171 | System Too Lean (Bank 1) |
| P0174 | System Too Lean (Bank 2) |
| P0335 | Crankshaft Position Sensor A Circuit |
Guides that help
- engine sputtering
- spark plug wires
- engine misfire and flashing check engine light
- bad ignition coil symptoms
- bad spark plug symptoms
- rough idle causes
- vacuum leak
- compression and leak-down tests
When it is more than a sensor
If a compression or leak-down test shows a burnt valve, broken ring or failed head gasket, the decision becomes repair versus replacement; see engine replacement cost and compare engines by code on our engines page.
More guides: check engine light flashing.
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