P0302

What P0302 means

Your engine's computer tracks how fast the crankshaft spins between each cylinder firing. When cylinder 2 isn't contributing power the way it should, on one firing or repeatedly, the crank speed dips and the computer logs a misfire on that specific cylinder. The code doesn't tell you why cylinder 2 is misfiring, only that it is. That's the part people get wrong when they read this code off a scanner and go straight to buying a coil or a set of spark plugs.

Is it safe to drive

Depends on how the misfire is behaving. If the check engine light is steady and the car drives normally, you can generally still get around, but you should get it looked at soon. If the light is flashing, that means the misfire is bad enough that unburned fuel is being dumped into the exhaust, where it can overheat and damage the catalytic converter. A flashing light means stop driving it and get it towed or trailered in, not driven in. Either way, watch for rough idle, a hesitation or stumble under acceleration, and a noticeable loss of power.

What commonly causes it

Roughly in order of how often we see it:

Spark plug worn out or fouled on cylinder 2 — the most common cause on higher mileage cars.
Ignition coil weak or failed, either a coil-on-plug for that cylinder or a shared coil pack, depending on the engine.
Fuel injector on that cylinder clogged, weak, or electrically failing.
Vacuum leak or intake gasket leak affecting that cylinder's air-fuel mix.
Low compression on cylinder 2, from a worn ring, a valve issue, or in worse cases a blown head gasket.
Wiring or connector problem to the coil or injector on that cylinder.

Which of these is likely depends a lot on the engine. Some engines are known for coil packs failing early, others have injector issues, others are more prone to intake gasket leaks. There isn't one answer that fits every car, which is part of why guessing at parts gets expensive fast.

Diagnosis and rough cost

A proper diagnosis starts with pulling stored and pending codes, then usually swapping the spark plug and coil from cylinder 2 with a known-good cylinder to see if the misfire moves. If it doesn't move, we look at fuel delivery and compression on that cylinder specifically. This takes real shop time, generally somewhere in the range of one to two hours of diagnostic work before we can tell you what's actually wrong.

Cost to fix varies a lot depending on what's found. A bad plug or coil is a relatively minor repair. A compression problem or a head gasket is a much bigger job. We won't know which one you've got, or give you a number, until we've actually tested cylinder 2 rather than guessed at it.