Cylinder 1 Misfire Detected
Cylinder 1 isn't firing properly, causing incomplete combustion—like one cylinder in your engine is misfiring while the others work fine. This disrupts smooth engine operation and increases emissions.
The ECU monitors crankshaft speed variation between cylinder firings using the crankshaft position sensor. When cylinder 1 fires, the engine accelerates slightly; if that acceleration is missing or delayed, the ECU detects a misfire. The system counts misfire events over a drive cycle and triggers a fault when thresholds are exceeded.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Crankshaft acceleration (Cyl 1) | Expected RPM rise within 10ms of spark event | Insufficient or delayed RPM rise detected across multiple combustion cycles |
| Misfire count per 1000 revolutions | 0-2 misfires acceptable | ≥3 misfires triggers P0302 |
Code P0302 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, P0302 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.