Code guide
P0302 — cylinder 2 misfire
The code names the cylinder, which narrows the cause to something on that cylinder specifically — spark, fuel, or compression. On some engines there's a wrinkle worth checking first: whether cylinder 2 shares an ignition coil with a neighbour.
Cylinder 2 · Misfire · P0301, P0303–P0312 are the same fault on other cylinders
The short version
If your check engine light is FLASHING, stop driving as soon as you safely can. A flashing light during a misfire means unburned fuel is reaching the catalytic converter, which it can destroy within minutes.
P0302 means the misfires were on cylinder 2 specifically, not spread across the engine. The last digit of a P030x code is the cylinder number, so this is the direct sibling of P0301 (cylinder 1) — everything about how to diagnose an isolated single-cylinder misfire is the same, just aimed at a different cylinder.
Because the fault is isolated, the cause lives on that cylinder: its spark, its fuel delivery, or its compression. There is one thing worth checking before any of those, though — on some engines, cylinder 2 doesn't light its own coil alone.
Reading codes, clearing them, and watching live data are all free in Fixiom — always, no credits and no subscription.
Does it share a coil with another cylinder?
Most modern engines use coil-on-plug ignition: one independent coil sitting right on top of each spark plug. On those, a P0302 is entirely a cylinder-2 story and the pairing question below doesn't apply.
Plenty of engines — especially four-cylinders built through the 2000s, and some V6s — use waste-spark (distributorless) ignition instead: one coil fires two spark plugs at once, one of them on the correct compression stroke and the other harmlessly on its exhaust stroke. On the common inline-4 firing order, the companion pairs are usually cylinders 1 & 4 sharing one coil and cylinders 2 & 3 sharing another — though the exact pairing is engine-specific, and it's worth confirming for yours before assuming.
Why this matters for P0302: if your engine uses waste spark and cylinder 2 pairs with cylinder 3, a failing shared coil can misfire either cylinder, or both. That's exactly the scenario P0303 walks through — including how to tell "one bad coil" apart from "two separate cylinder problems" using which codes show up together.
If P0302 is the only misfire code, and your engine uses waste spark, that leans away from the shared coil (a dying shared coil more often drags its partner along at least intermittently) and toward something local to cylinder 2 alone.
The swap test, in brief
Because the fault names a cylinder, there's a genuinely conclusive test available: move the suspect coil or plug to a different cylinder, clear the code, drive it the way it normally misfires, and re-scan. If the code follows the part to its new cylinder, you've found it. If cylinder 2 keeps misfiring anyway, that part was fine.
P0301's full swap-test walkthrough covers the procedure step by step, how to read each outcome, and the caveat about confirming which physical cylinder is "2" before you move anything — all of it applies here without any changes.
Likely causes, in order
- Ignition coil for cylinder 2 — and on a waste-spark engine, check whether its paired cylinder is showing anything too before you buy just one.
- Spark plug for that cylinder — worn past its gap, cracked, or fouled.
- Fuel injector for cylinder 2 — clogged, leaking, or electrically failing.
- A vacuum leak local to that cylinder's intake runner.
- Low compression on cylinder 2 — the mechanical answer, once spark and fuel are eliminated.
- Wiring or a connector at that cylinder's coil or injector.
Which one is cylinder 2?
Not a safe guess by looking. Numbering follows the engine's own convention and varies by manufacturer and layout — on an inline engine it's usually sequential from one end, but which end, and which bank is which on a V-engine, isn't something to assume. Confirm it for your specific engine in service information before swapping or removing anything.
What a phone can't see
What it genuinely gives you: the code naming the cylinder, freeze frame conditions from when it set, per-cylinder misfire counts under Mode 06 (useful for spotting a paired cylinder quietly accumulating counts of its own), live data while it misfires, and clear-and-re-scan for the swap test.
What it cannot do: a compression or leakdown test, inspecting a spark plug, bench-testing a coil, or doing the physical swap for you. Live data narrows it to a short list and a test procedure; hands on the car confirm it.
Common questions
What does P0302 mean?+
The engine computer detected misfires specifically on cylinder 2. The last digit of the code is the cylinder number. Because the fault is isolated to one cylinder, the cause is almost always a component on that cylinder — spark, fuel, or compression — rather than something the whole engine shares.
Can a bad ignition coil on another cylinder cause P0302?+
On engines with coil-on-plug ignition, no — each cylinder has its own independent coil. On engines with waste-spark (distributorless) ignition, one coil often fires two cylinders together, and a failing shared coil can misfire either or both. Check whether your engine uses that setup, and whether the paired cylinder is showing anything too.
How do I confirm it's the coil and not the spark plug?+
Swap the coil with a known-good one from a neighbouring cylinder, clear the code, drive it the way it normally misfires, then re-scan. If the code follows the part, that part was the problem. If cylinder 2 keeps misfiring, move to the next suspect.
Can I drive with a P0302?+
A steady light is generally not an emergency, though worth diagnosing promptly. A flashing light is different — that means an active misfire is putting raw fuel into the exhaust, which can destroy the catalytic converter within minutes. Stop driving as soon as it's safe.
Related guides
- P0301 — Cylinder 1 misfire — and the swap test that proves the cause in one drive.
- P0303 — Cylinder 3 misfire — and how a second code on its partner cylinder changes the diagnosis.
- P0300 — Random misfire — and the per-cylinder counters that show which one it really is.
- Check engine light flashing — A flashing light is not the same warning as a steady one. What to do right now.
The code names the cylinder. The coil layout tells you if it's alone.
Codes, freeze frames, live data, and Mode 06 misfire counts are free in Fixiom — always. Confirm before you buy the part.