Ignition and misfire

P0302Cylinder 2 misfire detected

Cylinder 2 Misfire Detected

Stop driving or get it looked at now

Generic OBD-II code

Ignition/Combustion System (Misfire Monitor)

What this part does

The engine control module monitors crankshaft speed fluctuations to detect a cylinder that is not firing or burning fuel completely; the underlying cause is usually ignition, fuel delivery, or mechanical (compression/valve-train).

What the computer is measuring

Every cylinder that fires accelerates the crankshaft very slightly, and the crankshaft position sensor is fast enough to see each one individually. The computer knows the firing order and where the engine is in it, so a missing contribution can be attributed to a specific cylinder rather than just counted.

P0302 means those misses were traced to cylinder number two, using the manufacturer’s numbering. That numbering is not always the order you would guess by looking at the engine, particularly on a V configuration, so confirm which physical cylinder is number two before you remove anything.

The value of a cylinder specific code is that it reduces the problem to four things that belong to that cylinder alone: the coil, the plug, the injector and the compression. The first three can be swapped with a neighbouring cylinder, and if the fault moves with the part you have your answer without a meter or a scope.

Do read the plug rather than binning it. A plug that is dry and simply worn tells a different story from one that is wet with fuel, black and sooty, oily, or crusted with white deposits. Those deposits are the cheapest diagnostic information on the whole engine.

What you will notice

  • Flashing check engine light during the misfire. Stop driving when it flashes.
  • Shaking or stumbling at idle.
  • Hesitation and lost power under load.
  • Poor fuel economy and a raw fuel smell from the exhaust.

Likely causes, most common first

Ordered by how often each one actually turns out to be the problem, not alphabetically and not by part price.

  1. A failed ignition coil on cylinder 2

    The usual answer on a coil on plug engine, and provable in minutes by swapping it.

  2. A worn or fouled spark plug

    Read it before discarding it. Oil fouling, coolant deposits and a widened gap each point somewhere different.

  3. A clogged or failed fuel injector on cylinder 2

    Produces the same symptom as an ignition fault and needs the same swap test to separate them.

  4. Low compression in cylinder 2

    Burnt valve, worn rings or a head gasket. Confirm with a compression test rather than by continuing to replace parts.

  5. A vacuum leak feeding that one cylinder

    A cracked intake runner or a failed gasket at one port leans that cylinder out enough to miss while the others stay normal.

What to check, in order

  1. Swap the cylinder 2 coil with a neighbouring one, clear the codes and drive the vehicle.

    A code that moves to the other cylinder is a failed coil. A code that stays on cylinder 2 rules the coil out entirely.

  2. Swap the spark plug the same way, and read the old one as you remove it.

    A misfire following the plug is the plug. Oil on the plug points at valve stem seals or rings rather than ignition at all.

  3. Compare injector operation across the cylinders.

    A silent or noticeably different injector explains the misfire. Even operation across all of them leaves compression.

  4. Compression test cylinder 2 against its neighbours.

    A significant shortfall confirms a mechanical fault and stops the parts replacement.

Where this one turns up most

  • Engines at or past the spark plug service interval.
  • Vehicles where one coil has already been replaced, since the rest are usually the same age.

Codes that often show up alongside it

What a DriveDecode adapter can read

A DriveDecode adapter reads engine and emissions systems: the powertrain and emissions codes the OBD-II standard requires on every US vehicle it covers. It does not read ABS, airbag (SRS), TPMS or transmission-specific manufacturer codes. Those need make-specific decoding that generic OBD-II hardware cannot do.

Reading P0302 on your own car

DriveDecode pulls P0302 straight off the vehicle along with the freeze frame the computer stored when it set: the coolant temperature, engine load and speed at that exact moment. That context is what separates a fault that happens on a cold start from one that happens under load, and it is the first thing the list above asks you to narrow down.

See how DriveDecode works

Last reviewed 2026-09-05. Definition sourced from the published standard.