Cylinder 5 Misfire Detected
Cylinder 5 isn't firing properly—like one spark plug in a fireworks display is misfiring. The engine's computer detected that this cylinder isn't combusting fuel at the right time or with enough power.
The ECU monitors crankshaft speed variation and ignition timing by comparing cylinder-to-cylinder combustion events. When cylinder 5's contribution drops below the expected threshold over multiple cycles, a misfire is detected.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Crankshaft acceleration rate | Consistent within ±2% across all cylinders | Cylinder 5 drops >3% below baseline |
| Combustion event frequency | Regular ignition pulses per revolution | Missing or delayed ignition signature on cylinder 5 |
Code P0306 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, P0306 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.