Cylinder 12 Misfire Detected
The engine's computer detected that cylinder 12 isn't firing properly, like a car with a dead spark plug that causes a stumble. This misfiring reduces power and increases emissions.
The ECM monitors crankshaft speed variations using the crank sensor to detect misfires. When a cylinder fails to fire, it creates a distinct dip in RPM that the ECU recognizes as a misfire event. If misfire counts exceed the threshold, the fault code sets.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Crankshaft acceleration variance | Consistent RPM without dropouts | >2-4% RPM deviation per cylinder event |
| Cumulative misfire count | <2 misfires per 1000 revolutions | >4 misfires per 1000 revolutions |
Code P0320 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, P0320 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.