# P0302: Cylinder 2 Misfire Detected **Verdict:** Drive to a shop this week Ignition and misfire - Generic OBD-II code, applies to all gasoline cars and light trucks sold in the US since 1996. - **Typical cost:** $100-$1,500 - **Urgency:** This week - **Most likely:** Coil, plug or oil in the plug well - **DIY?:** Steps 1-3 ## Quick answer P0302 means cylinder 2 is misfiring, so it is not making its share of power. Ignition coil and spark plug problems are the most frequent cause. On some engines, oil leaking into the spark plug well from a bad valve cover gasket shorts out the coil. ## What does P0302 mean? Cylinder 2 is numbered by the maker's own scheme, so where it sits depends on the engine. On most inline four-cylinder engines it is the second cylinder from the timing belt or chain end. On many GM and Chrysler V8s it is the front cylinder of the passenger-side bank, while Ford V8s put it second on the same bank as cylinder 1. Subaru boxer engines place it at the front of the driver's side, and Honda V6s put it on the rear bank. The computer identifies cylinder 2 by timing each crankshaft slowdown against the firing order. P0302 sets when those slowdowns exceed a calibrated rate: a rate that threatens the catalytic converter flashes the light and can set the code at once, while a lower, emissions-level rate normally needs two drive cycles. On older waste-spark engines, cylinders 2 and 3 often share one coil, which changes how you test it. ## What are the symptoms of P0302? - Check engine light on, sometimes flashing - Rough idle and vibration - Engine stumbles when accelerating - Lower fuel economy ## What causes P0302? Ranked from most to least likely. Check them in this order: the cheap, common causes first. 1. **Failing ignition coil on cylinder 2** (most common). Ignition coils break down from heat and vibration, and the boot that meets the plug can crack or soften. When the cylinder 2 coil weakens, the misfire often starts under load, then becomes constant. On coil-on-plug engines, swapping the cylinder 2 coil with cylinder 1 or 3 and seeing the code change to P0301 or P0303 confirms it. 2. **Worn or fouled spark plug** (common). As the cylinder 2 plug wears, its gap widens and it needs more voltage to fire, so it misfires first during acceleration or highway passing. Oil fouling, heavy carbon or a cracked insulator do the same. Engines past their plug interval are the usual candidates. Compare its gap and deposits with the cylinder 1 or 3 plug. 3. **Oil in the spark plug well** (less common). On engines where the plug sits in a deep tube through the valve cover, a hardened cover gasket or tube seal lets oil fill the well. Oil softens the coil boot and lets spark leak to ground, so cylinder 2 misfires. Many four-cylinder engines, including several Honda and Toyota designs, use this layout. A wet, oily plug well confirms it. 4. **Faulty cylinder 2 fuel injector** (less common). If the coil and plug are good, the cylinder 2 injector may be clogged, leaking or electrically dead. A clogged injector leans the cylinder out, usually worst at idle; a leaking one floods it and can cause a rough start after sitting. A noid light checks the pulse, and swapping injectors with a neighbor shows whether the misfire follows. 5. **Low compression in cylinder 2** (rare). If the misfire stays on cylinder 2 after coil, plug and injector checks, a mechanical fault is likely: a burnt or bent valve, worn rings, or a head gasket leaking between cylinders 1 and 2 or into the coolant. Higher-mileage or previously overheated engines are most at risk. A compression test, then a leak-down test, shows where pressure escapes. ## How do you diagnose P0302? 1. Locate cylinder 2 for your engine with a diagram; numbering differs between makes. 2. Pull the cylinder 2 coil and check the well and boot for oil or carbon tracks. 3. Swap the cylinder 2 coil with cylinder 1 or 3; if the code changes to that cylinder, replace the coil. 4. Inspect or swap the spark plug, then check the injector with a scan tool or noid light. 5. Do a compression test on cylinder 2 if the misfire stays put. ## How do you fix P0302, and what does it cost? | Fix | Typical cost | What it involves | | --- | --- | --- | | Replace the cylinder 2 ignition coil | $150-$350 | Includes the part and a short labor charge. | | Replace spark plugs and fix oil leak | $250-$650 | Plugs plus a valve cover gasket or tube seals if oil is getting into the well. | | Replace the cylinder 2 fuel injector | $250-$700 | When testing shows the injector is not working right. | Full price breakdowns: [ignition coil replacement cost](/cost/ignition-coil-replacement), [spark plug replacement cost](/cost/spark-plug-replacement), [valve cover gasket replacement cost](/cost/valve-cover-gasket-replacement). ## Is it safe to drive with P0302? > **Drive to a shop this week.** With a steady check engine light, drive gently to a shop. A flashing light means stop, because unburned fuel can overheat the catalytic converter. ## Will P0302 fail an emissions test? Most state OBD inspections fail any vehicle with the check engine light commanded on, so P0302 must be fixed first. Cylinder 2 misfires also push unburned fuel into the converter, raising hydrocarbon readings in states that still sniff the tailpipe. Clearing the code resets readiness monitors, so allow several days of normal driving before the retest. ## After the repair: clearing P0302 If oil was found in the plug well, check after a few drives that the new valve cover gasket or tube seal is dry, because returning oil will ruin the new coil. Clear the code and watch the cylinder 2 misfire counter on a scan tool at idle and under light acceleration. Zero counts after a week mean the repair held. ## How to prevent P0302 - Fix valve cover oil leaks early, before oil collects in the cylinder 2 plug well. - Replace spark plug tube seals whenever the valve cover gasket is replaced on engines that use them. - Torque spark plugs to specification so the cylinder 2 plug seals and sheds heat properly. - Replace plugs as a full set at the maker's interval rather than one at a time. - Inspect coil boots for oil softening or cracks each time the plugs are serviced. ## Codes often seen with P0302 - [P0300](/codes/p0300): Random/Multiple Cylinder Misfire Detected - [P0301](/codes/p0301): Cylinder 1 Misfire Detected - [P0303](/codes/p0303): Cylinder 3 Misfire Detected - [P0420](/codes/p0420): Catalyst System Efficiency Below Threshold (Bank 1) ## Frequently asked questions ### Can oil in the spark plug well cause P0302? Yes, oil in the spark plug well can cause P0302. It softens the coil boot and lets spark leak to ground instead of firing the plug. The fix is a new valve cover gasket or tube seal, plus a new coil or plug if the oil has already damaged them. ### Is P0302 expensive to fix? Usually not; most fixes cost $150 to $450 for a coil or a set of spark plugs. Adding a valve cover gasket for an oil leak brings it to about $250 to $650. It gets expensive only if the injector or internal engine parts such as valves or the head gasket are at fault. ### How long can I drive with P0302? Not long; aim to fix it within days. Every misfire sends unburned fuel into the exhaust, which can overheat the catalytic converter, and an oil-soaked coil usually gets worse. Stop driving and arrange a tow if the check engine light starts flashing or the engine shakes hard. ### Where is cylinder 2? On most inline four-cylinder engines, cylinder 2 is second from the timing belt or chain end. On many GM and Chrysler V8s it is the front cylinder on the passenger side, on Ford V8s it is second on the passenger side, and on Subaru boxers it is the front cylinder on the driver's side. ### What do I swap the cylinder 2 coil with? Swap it with cylinder 1 or 3, whichever is easier to reach, staying on the same bank on a V engine. Clear the code and drive until the misfire returns. If the new code is P0301 or P0303, the coil you moved is bad; if it stays P0302, check the plug next. ### What if my engine uses a coil pack instead of individual coils? On waste-spark engines, one coil pack fires cylinders in pairs, and on most four-cylinders cylinders 2 and 3 share a coil. A bad coil usually misfires both, so P0302 alone points more to the plug, plug wire or injector. Swapping the cylinder 2 and 3 plug wires shows whether the wire is to blame. ### Why does P0302 come back after replacing the coil? If P0302 returns after a new coil, the coil probably was not the root cause. Check whether oil is still entering the plug well, whether the plug is the correct type and gap, and whether the connector is fully latched. If those are fine, test the injector and run a compression test. ### Can I fix P0302 myself? Often yes, if the cause is the coil or plug and cylinder 2 is easy to reach, as on most inline four-cylinders. Basic tools and a torque wrench are enough. Subaru boxer plugs are tight to reach, and some transverse V6s put cylinder 2 on the rear bank, which may make it a shop job. ### Will P0302 pass an emissions test? No, an active P0302 with the light on fails an OBD-based emissions test in most states. Fix the misfire, clear the code and drive several days of mixed trips so the readiness monitors finish. Check them with a scan tool before you go, because a car with too many incomplete monitors is turned away. ### Can P0302 damage the catalytic converter? Yes, if it continues. Each cylinder 2 misfire sends unburned fuel into the exhaust, where it burns inside the converter and drives its temperature up. A flashing light means that heat is already high enough to cause damage. Fixing the misfire promptly costs far less than a new converter. ## Sources - [SAE J2012: Diagnostic Trouble Code Definitions](https://www.sae.org/standards/content/j2012_201812/) ## Other ignition and misfire codes - [P0300 Random/Multiple Cylinder Misfire Detected](https://diagxcar.com/codes/p0300) - [P0301 Cylinder 1 Misfire Detected](https://diagxcar.com/codes/p0301) - [P0303 Cylinder 3 Misfire Detected](https://diagxcar.com/codes/p0303) - [P0304 Cylinder 4 Misfire Detected](https://diagxcar.com/codes/p0304) - [P0305 Cylinder 5 Misfire Detected](https://diagxcar.com/codes/p0305) - [P0306 Cylinder 6 Misfire Detected](https://diagxcar.com/codes/p0306) - [P0307 Cylinder 7 Misfire Detected](https://diagxcar.com/codes/p0307) - [P0308 Cylinder 8 Misfire Detected](https://diagxcar.com/codes/p0308) - [P0316 Engine Misfire Detected on Startup (First 1000 Revolutions)](https://diagxcar.com/codes/p0316) - [P0320 Ignition/Distributor Engine Speed Input Circuit](https://diagxcar.com/codes/p0320) - [P0352 Ignition Coil "B" Primary/Secondary Circuit](https://diagxcar.com/codes/p0352) ## Symptoms - [Why is my car idling rough?](https://diagxcar.com/symptoms/rough-idle) - [Why does my car hesitate when I accelerate?](https://diagxcar.com/symptoms/car-hesitates-when-accelerating) - [Why does my car shake at idle?](https://diagxcar.com/symptoms/car-shakes-at-idle) - [Why does my car shake when I accelerate?](https://diagxcar.com/symptoms/car-shakes-when-accelerating) ## Repair costs - [Ignition coil replacement cost](https://diagxcar.com/cost/ignition-coil-replacement): $150-$400 - [Spark plug replacement cost](https://diagxcar.com/cost/spark-plug-replacement): $120-$450 - [Valve cover gasket replacement cost](https://diagxcar.com/cost/valve-cover-gasket-replacement): $200-$800 --- Source page: https://diagxcar.com/codes/p0302 Updated: 2026-11-03 General information, not a substitute for a qualified mechanic.