P0302 code: Cylinder 2 Misfire Detected
What Is the P0302 Code?
P0302 means your engine’s control module detected a misfire specifically in cylinder 2. If you’ve already read about P0300 — the random misfire code — think of P0302 as the more specific version. The ECM knows exactly which cylinder is skipping, and it’s pointing at cylinder 2.
A misfire happens when the air-fuel mixture in that cylinder fails to combust properly. Cylinder 2 fires out of sequence, the engine loses a power stroke, and you feel it — rough idle, shaking, hesitation. The cause is almost always ignition, fuel, or compression related.
The good news is that a specific cylinder code is easier to diagnose than a random one. You know where to start.
What You’ll Notice
- Check engine light on — may be flashing in severe cases
- Rough, uneven idle
- Engine vibration or shaking
- Hesitation when accelerating
- Loss of power, especially at lower RPMs
- Increased fuel consumption
- Occasional misfire stumble at cruising speed
A flashing check engine light means the misfire is severe enough to damage the catalytic converter in real time. Don’t drive on a flashing light any further than necessary.
Where Is Cylinder 2?
Cylinder locations vary by engine layout:
- Inline 4-cylinder: Cylinder 2 is the second from the front of the engine
- Inline 6-cylinder: Second from the accessory belt end
- V6 / V8: Typically the second cylinder on the driver’s side bank — confirm in your service manual
Locating cylinder 2 before you start pulling components saves time and prevents mistakes.
What Usually Causes P0302
1. Worn or fouled spark plug in cylinder 2 The most common cause. Spark plugs have a service life, and when cylinder 2’s plug is worn, it misfires — sometimes intermittently at first, then consistently. A plug contaminated with oil or carbon also fails to fire reliably.
2. Failed ignition coil on cylinder 2 Each cylinder on most modern engines has its own coil-on-plug unit. When cylinder 2’s coil starts to fail, the spark becomes weak or inconsistent. Unlike P0301, where cylinder 1 is the target, here the coil swap test points you at cylinder 2’s coil specifically.
3. Faulty fuel injector on cylinder 2 A clogged or failed injector can’t deliver the right fuel quantity to cylinder 2. Too little fuel causes a lean misfire. A failed injector that doesn’t open at all causes a complete misfire every cycle.
4. Low compression in cylinder 2 Worn piston rings, a burnt exhaust valve, or a head gasket leak affecting cylinder 2 can drop compression below what’s needed for proper combustion. If compression is the cause, you’ll likely notice the misfire is consistent and doesn’t respond to plug or coil replacement.
5. Vacuum leak near cylinder 2 An intake manifold gasket leak or a cracked vacuum hose near cylinder 2 allows unmetered air in, leaning out the mixture in that specific cylinder and triggering P0302.
6. Cracked distributor cap or failing plug wire (older vehicles) On older engines with a distributor system, a cracked cap or a failing spark plug wire to cylinder 2 can cause intermittent or complete misfires on that cylinder.
How Serious Is P0302?
Serious — don’t put it off.
Unburned fuel from a misfiring cylinder enters the exhaust and burns inside the catalytic converter. Every misfire cycle accelerates converter damage. A catalytic converter replacement is significantly more expensive than the ignition components that typically cause P0302.
Beyond the cat, sustained misfiring puts mechanical stress on engine components. The longer it runs, the more wear accumulates.
How to Diagnose P0302
Step 1 — Read all stored codes
Confirm P0302 with your scanner. Check whether P0300 or other cylinder-specific codes are stored alongside it. Multiple codes can reveal whether the problem is isolated to cylinder 2 or affecting the whole engine.
Step 2 — Inspect the cylinder 2 spark plug
Remove the plug from cylinder 2 and compare it to the others. A plug that looks different from the rest — fouled, oil-coated, heavily worn, or blistered — tells you something specific is happening in that cylinder. Replace it and retest before going further.
Step 3 — Swap the ignition coil
Move the cylinder 2 coil to another cylinder — cylinder 4 is a common choice. Clear the codes and drive. If the misfire moves to P0304, the coil is the problem. If P0302 stays on cylinder 2, the coil is fine and you look elsewhere.
Step 4 — Test the fuel injector
Listen to cylinder 2’s injector with a mechanic’s stethoscope while the engine runs — a healthy injector makes a steady rhythmic click. A dead or weak injector sounds different or silent. Resistance testing with a multimeter confirms whether the injector is within spec.
Step 5 — Check for vacuum leaks near cylinder 2
With the engine idling, use carburetor cleaner carefully around the intake gaskets and vacuum lines near cylinder 2. A change in idle when you spray a specific spot pinpoints the leak. A smoke test done by a shop is a cleaner, safer alternative.
Step 6 — Compression test
If plugs, coil, and injector all check out, test compression in cylinder 2. A reading significantly lower than the other cylinders — or below the manufacturer’s minimum — means an internal engine problem is the root cause.
How to Fix P0302
Replace the spark plug — The first stop. Replace the cylinder 2 plug, and inspect the others while you’re at it. Plugs wear together, and one bad one usually means the rest are close behind.
Replace the ignition coil — Confirmed with the swap test. Replace the faulty coil — don’t swap it back.
Clean or replace the fuel injector — A quality fuel system cleaner handles mild clogs. A confirmed dead injector needs replacement.
Repair vacuum leaks — Replace cracked hoses and failed gaskets. The intake manifold gasket is more labor-intensive but straightforward for an experienced mechanic.
Engine repair — If compression is low, the repair depends on what’s causing it. A burnt valve requires head work. Worn rings are an engine rebuild. Get a proper assessment before spending money here.
What It Might Cost
| Repair | Estimated Cost |
|---|---|
| Spark plug replacement | $20 – $150 |
| Ignition coil replacement | $80 – $300 |
| Fuel injector cleaning | $50 – $150 |
| Fuel injector replacement | $150 – $400 |
| Vacuum leak repair | $100 – $400 |
| Head work / engine repair | $500 – $2,500+ |
Costs vary by vehicle make, model, and labor rates in your area.
Related Codes
- P0300 — Random/Multiple Cylinder Misfire Detected
- P0301 — Cylinder 1 Misfire Detected
- P0303 — Cylinder 3 Misfire Detected
- P0304 — Cylinder 4 Misfire Detected
- P0352 — Ignition Coil B Primary/Secondary Circuit Malfunction
- P0202 — Injector Circuit Malfunction Cylinder 2
Frequently Asked Questions
Can I drive with P0302? If the light is steady, short necessary trips are possible — but get it fixed soon. If the light is flashing, stop driving beyond what’s essential. You’re damaging the catalytic converter with every kilometre.
How is P0302 different from P0300? P0300 means misfires are happening but the ECM can’t identify a single cylinder as the cause. P0302 means cylinder 2 is specifically and consistently misfiring. P0302 is easier to diagnose because you know exactly where to look.
I replaced the plug and the code came back. What now? Move to the coil. Do the coil swap test — it takes ten minutes and tells you definitively whether the coil is the problem. If the misfire moves cylinder when you move the coil, you have your answer.
Can a bad injector cause P0302? Yes. A clogged injector that can’t deliver enough fuel causes a lean misfire on that specific cylinder. A completely dead injector causes a misfire on every cycle. If plug and coil are fine, the injector is the next thing to test.
What happens if P0302 is left unrepaired? Catalytic converter damage is the immediate risk — and replacement is expensive. Beyond that, the engine sustains abnormal mechanical stress from the uneven combustion. Fix it early and the repair is usually cheap. Leave it and it gets complicated.
This guide is for informational purposes only. For an accurate diagnosis, always consult a qualified mechanic.
