Random/Multiple Cylinder Misfire Detected
Your engine is misfiring randomly across multiple cylinders, like a few cylinders aren't firing properly on their turn. This causes power loss and rough running as combustion fails intermittently.
The ECU monitors crankshaft speed variation between cylinder firings using the crank sensor. When a cylinder misfires, it causes a slight drop in rotational acceleration. The ECM counts misfire events per 1000 revolutions and triggers P0301 when misfire rate exceeds the threshold.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Misfire count per 1000 revolutions | 0-2 misfires | 3+ misfires detected |
| Crankshaft acceleration variance | ±2% variation | Deviation >5% between cylinders |
Code P0301 is a moderate fault. You can generally drive to a workshop, but avoid long trips or high-load driving (motorway, uphill towing) until it is diagnosed. If the code keeps returning after clearing, or if you notice the symptoms listed above worsening, do not delay professional diagnosis. Many moderate codes have multiple possible root causes — a mechanic with live OBD data can identify the exact fault more efficiently than part-by-part trial and error.
Once the fault is repaired, P0301 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.
The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.