If the light is steady, drive gently to a shop soon — sustained misfire wastes fuel and slowly harms the catalytic converter. If the light is flashing, stop and shut off as soon as it is safe, because a hard misfire can destroy the cat quickly. P0302 means the engine control module has detected a misfire on cylinder 2 specifically — that cylinder is repeatedly failing to burn its air/fuel charge cleanly. The PCM sees it as a momentary loss of crankshaft speed each time cylinder 2 should fire, and once the rate crosses an emissions threshold it stores the code and lights the check-engine lamp.
What P0302 means
The PCM detects misfire by watching crankshaft rotational speed through the crankshaft position sensor, referenced to the camshaft sensor so it knows which cylinder is in its power stroke. Every good combustion event gives the crankshaft a tiny acceleration; a misfire produces a measurable deceleration at cylinder 2's firing position, and the module counts those events over a rolling window of engine revolutions. When cylinder 2's misfire rate is high enough to raise tailpipe emissions past the calibrated limit, the code sets as P0302. Because the fault is isolated to one cylinder, the problem is almost always in that cylinder's own ignition, fuel, or mechanical hardware rather than something shared by the whole engine.
Symptoms
- Steady check-engine light, or a flashing/blinking check-engine light when the misfire is severe enough to threaten the catalytic converter
- Rough, shaky idle and a noticeable engine vibration you can often feel through the seat or steering wheel
- Stumble, hesitation or loss of power under acceleration, sometimes with a rhythmic 'skip' at cruise
- Higher fuel consumption and a rotten-egg or raw-fuel smell from unburned mixture reaching the exhaust
- Occasional popping or spitting from the intake or exhaust, and hard starting or a brief stall on cold start
Common causes
- Failed or weak ignition coil on cylinder 2 (coil-on-plug 'B') — the single most common cause on modern engines
- Worn, fouled, cracked or wrong-gap spark plug in cylinder 2, including carbon tracking on the plug or boot
- Clogged, leaking or electrically open fuel injector for cylinder 2, or an open/shorted injector-control circuit
- Loss of compression on cylinder 2 from a burned or leaking valve, worn rings, a bent valve or a leaking head gasket
- Vacuum or intake leak feeding extra unmetered air to that cylinder, leaning out its mixture
- Damaged wiring, a corroded connector, or a broken ground on cylinder 2's coil or injector circuit
- Carbon-tracking or a hairline crack in the coil boot letting spark arc to ground before it reaches the plug
- Low or high fuel-rail pressure, contaminated fuel, or (rarely) a PCM driver fault affecting that cylinder
Severity & driving advice
Severity: Moderate — A steady light is usually drivable short-term, but a flashing check-engine light means catalyst-damaging misfire — stop soon to protect the converter.
Can I drive? If the light is steady, drive gently to a shop soon — sustained misfire wastes fuel and slowly harms the catalytic converter. If the light is flashing, stop and shut off as soon as it is safe, because a hard misfire can destroy the cat quickly.
Diagnostic approach
- Read all codes and the freeze-frame data — Pull every stored code, not just P0302. If lean codes (P0171/P0174) or fuel-trim codes are present with it, chase a vacuum/fuel-delivery problem first; if only P0302 is stored, focus on cylinder 2's own hardware. Record the freeze-frame RPM, load and coolant temp so you can reproduce the conditions that set it — misfires detected on deceleration in particular point toward a mechanical fault.
- Watch the misfire-counter data live — On a scan tool, view the per-cylinder misfire monitor and confirm the counts are accumulating on cylinder 2. Note that the PCM will shut down the injector for a cylinder it sees badly misfiring to protect the catalyst, so a completely dead cylinder can read zero fuel there. Drive under the freeze-frame conditions to make the counts climb and verify the fault is genuinely isolated to cylinder 2.
- Swap the coil and plug to an adjacent cylinder — This is the fastest way to isolate the cause. Move cylinder 2's ignition coil to a neighbouring cylinder (and note its plug) and clear the code. If the misfire follows the coil to the new cylinder, the coil is bad; if the misfire stays on cylinder 2, the coil is good and the fault is in the plug, injector, wiring or the cylinder itself.
- Inspect the plug, coil boot and connectors — Remove the cylinder 2 spark plug and check for cracks, carbon tracking, foreign material, an out-of-spec gap, oil or fuel fouling, and a loose electrode — lightly tapping the plug should not move the centre electrode. Inspect the coil boot for carbon tracks or a hairline crack that lets spark arc to ground, and check the coil/injector connector for corrosion, spread terminals or a poor ground.
- Test injector 2 and fuel delivery — If the misfire stays on cylinder 2 with a known-good coil and plug, move to fuel. Compare injector 2's resistance and its click/wiring to the others, and check for a clogged or leaking injector. Verify fuel-rail pressure is within specification — for example, the 3.6L Pentastar target is about 58 psi (400 kPa ± 14 kPa / 2 psi); pressure that is low, high or leaking down can starve or flood the cylinder.
- Check cylinder 2 compression and for vacuum leaks — If ignition and fuel both test good, do a compression (and if needed a leak-down) test on cylinder 2 and compare it to the other cylinders; a low, uneven reading means a valve, ring, head-gasket or timing problem. Also inspect for intake and vacuum leaks near that runner, since unmetered air leaning one cylinder can misfire it. Only after all of this checks out should a PCM output-stage fault be considered.
Make & model notes
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FAQ
What is the difference between P0302 and P0300?
P0302 is a misfire the PCM has isolated to cylinder 2 alone, so the fault is almost always in that one cylinder's coil, plug, injector or compression. P0300 is a random or multiple-cylinder misfire the module could not pin to a single cylinder, which usually points to something shared by the whole engine — fuel pressure, a large vacuum leak, EGR, timing or bad fuel. It is common to see P0302 alongside P0300 when one cylinder is the worst offender.
Which cylinder is number 2, and can I just swap parts to find it?
Cylinder 2's physical location depends on your engine's firing order and layout, so check a cylinder-numbering diagram for your specific engine rather than assuming it is the second one you see. Once you have found it, swapping its coil (and plug) to an adjacent cylinder and clearing the code is the classic test: if the misfire moves with the coil, that coil is the culprit; if it stays on cylinder 2, the fault is the plug, injector or the cylinder's mechanicals.
Why is my check-engine light flashing with P0302?
A flashing (rather than steady) light means the misfire on cylinder 2 is severe enough that raw fuel is reaching the catalytic converter fast enough to overheat and damage it. The PCM measures the misfire rate over a short window of crankshaft revolutions and flashes the lamp when that catalyst-damaging threshold is crossed. Ease off the throttle and get off the road promptly — a converter can be ruined in a short drive under a hard misfire.
Can a vacuum leak or lean fuel condition cause P0302?
Yes. If an intake or vacuum leak sits near cylinder 2's runner, that cylinder gets extra unmetered air, runs lean and can misfire even when its coil, plug and injector are fine. Lean-mixture codes or high positive fuel trims stored alongside P0302 are a strong clue to look for a vacuum leak, a leaking intake gasket or an unmetered-air source before condemning ignition parts.
Is it safe to keep driving with P0302?
Briefly and gently, if the light is steady — but a misfire dumps unburned fuel into the exhaust, wastes fuel and slowly cooks the catalytic converter, so it should be fixed quickly. If the light is flashing, treat it as a stop-driving warning: continuing risks a converter failure that costs far more than the coil or plug that usually caused the misfire.