Cylinder 7 Misfire Detected
Cylinder 7 isn't firing properly, like one spark plug in an 8-cylinder engine misfiring intermittently. The engine computer detected the cylinder isn't contributing power strokes consistently.
The ECU monitors crankshaft acceleration using the crankshaft position sensor to detect when a cylinder fires. If cylinder 7 shows abnormally low acceleration during its power stroke compared to baseline, it registers a misfire. The ECM counts misfire events and sets a fault when threshold is exceeded.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Crankshaft acceleration variance | Consistent 3-5% variation between cylinders | >10% deviation on cylinder 7 over 200 revolution window |
| Misfire event count | 0-2 misfires per 1000 revolutions | >8 misfires per 1000 revolutions |
Code P0308 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, P0308 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.