P0302: Cylinder 2 Misfire Detected
TL;DR
P0302 = cylinder 2 misfire. Severity: high. STOP if the light is flashing (converter damage). Top causes: spark plug (35%), ignition coil (30%), injector or compression (35%). A quick test is to swap the coil/plug with a neighboring cylinder and see if the misfire follows.
Can I keep driving with P0302?
IF the light is steady → drive gently and fix it soon; a misfire wastes fuel and can foul the converter over time. IF the light is FLASHING → stop as soon as safe; an active misfire dumps raw fuel into the exhaust and can quickly ruin the catalytic converter.
Symptoms
- Check engine light (steady or flashing)
- Engine shaking / rough idle
- Loss of power and hesitation
- Worse fuel economy
- Occasional smell of unburned fuel
Top causes (ranked by probability)
| Likely cause | Probability | Notes |
|---|---|---|
| Worn or fouled spark plug (cylinder 2) | 35% | Cheapest first check |
| Clogged injector or low compression (cylinder 2) | 35% | |
| Failing ignition coil (cylinder 2) | 30% | Swap-test to a neighbor cylinder |
What does P0302 mean?
Technical explanation
The ECM detects misfires by monitoring tiny variations in crankshaft speed as each cylinder fires. P0302 sets when cylinder 2 exceeds the misfire-rate threshold. Because the fault is cylinder-specific, diagnosis focuses on that cylinder’s ignition (plug, coil, wiring), fuel (injector), and mechanical health (compression, valves). Swapping the coil or plug to an adjacent cylinder and seeing whether the code moves (e.g. to P0303) is a fast, definitive test.
In simple terms
Each cylinder is one of the engine’s "power chambers." P0302 means chamber number 2 keeps failing to fire properly, so the engine shakes and loses a bit of power. It’s usually that cylinder’s spark plug or ignition coil, and it’s easy to test by swapping parts with the cylinder next to it.
How to diagnose P0302 (step by step)
- Confirm the code and which cylinder. P0302 = cylinder 2; check for companion codes (lean/rich, P0300).
- Swap the coil to an adjacent cylinder. If the misfire moves with the coil, the coil is bad.
- Inspect/replace the spark plug. Look for wear, fouling or wrong gap on cylinder 2.
- Test the injector. Check that cylinder 2’s injector is firing and not clogged.
- Check compression. Low compression points to a mechanical fault (valves, rings).
Repair options & cost
- Replace the spark plug
- Replace the ignition coil
- Clean or replace the injector
- Repair the mechanical cause (valves/compression)
🔧 Doing it yourself? Buy the part: Spark plugs · Ignition coil
| DIY cost | $10–$150 |
|---|---|
| Workshop cost | $80–$500 |
| Repair time | 20 minutes (plug/coil) to several hours |
Costs are local ballpark ranges and vary by region and vehicle.
Tools you’ll need
Scan your car: recommended OBD-II scanners →Vehicle-specific notes
- Cylinder numbering varies by engine — confirm which physical cylinder is #2 for your vehicle.
- On coil-on-plug engines, swap-testing the coil is the fastest diagnosis.
- A repeat single-cylinder misfire after new plug/coil points to an injector or compression issue.
Common mistakes to avoid
- Replacing all coils when a swap-test would isolate the one bad coil
- Ignoring a flashing light and damaging the converter
- Overlooking a clogged injector or low compression
- Using the wrong spark-plug gap
Frequently asked questions
Can I drive with a P0302?
Briefly and gently if the light is steady, but not at all if it is flashing — an active misfire can destroy the catalytic converter. Fix it promptly.
How do I know if it’s the coil or the plug?
Swap the coil (and/or plug) from cylinder 2 to an adjacent cylinder. If the misfire moves to that cylinder, the part you moved is the culprit.
Where is cylinder 2?
It depends on the engine layout and firing order. Look up your specific engine’s cylinder numbering — it is not always the second one from the front.
P0302 summary
| Meaning | Cylinder 2 misfire |
|---|---|
| Severity | High |
| Safe to drive? | Caution — no if flashing |
| Top cause | Spark plug / coil |
| DIY cost | $10–$150 |
| Shop cost | $80–$500 |