P0302 — Cylinder 2 Misfire Detected

Generic OBD-II · all makesPowertrain (engine & transmission)

P0302 indicates that the powertrain control module has detected a misfire in cylinder 2. The engine’s combustion cycle in that cylinder is not completing properly, causing uneven power output.

Symptoms

Rough idle or engine vibration at low speeds
Loss of power or hesitation during acceleration
Engine shaking that intensifies when the vehicle is under load
Check Engine Light illuminated
Increased fuel consumption
Possible stalling when coming to a stop

What causes it — most likely first

1. Faulty spark plug in cylinder 2

A worn, fouled, or improperly gapped spark plug can fail to ignite the air‑fuel mixture.

2. Defective ignition coil for cylinder 2

A weak or failing coil will not provide sufficient voltage to the spark plug.

3. Bad fuel injector for cylinder 2

Clogged, leaking, or electrically failed injector prevents proper fuel delivery.

4. Low compression in cylinder 2

Worn piston rings, a damaged valve, or a head gasket leak can reduce compression enough to cause a misfire.

5. Vacuum leak affecting cylinder 2

A leaking intake manifold gasket or cracked vacuum hose can lean out the mixture for that cylinder.

6. Powertrain control module (PCM) malfunction

Rarely, the PCM may incorrectly register a misfire; this should be considered only after all mechanical and electrical causes are ruled out.

How it's diagnosed

Scan and clear the code, then perform a short‑term fuel trim test to see if cylinder 2 shows a large negative trim.
Inspect and, if necessary, replace the spark plug in cylinder 2; verify proper gap and torque.
Swap the ignition coil (or coil pack) from cylinder 2 with another cylinder and see if the misfire code follows the coil.
Perform a cylinder balance test or compression test on cylinder 2 to assess compression health.
Check fuel injector operation by listening for a click with a stethoscope or performing an injector flow test; replace if defective.
Inspect intake manifold gasket and vacuum lines for leaks near cylinder 2 and repair any found.

Code facts & related codes

SystemPowertrain (engine & transmission)

StandardizationSAE generic — identical on every make

Vehicles this code applies to

The definition is universal; the diagnostics are engine-specific. Open your vehicle for the codes documented for it:

2015 Honda Fit 1999 Lincoln Navigator 2000 Lincoln Navigator 2003 Ford Focus 2003 Mercury Marauder 2003 Ford Mustang 2004 Mercury Marauder

Frequently asked

Can a bad PCM cause P0302?

It is possible but uncommon. The PCM should be considered only after confirming that spark plugs, coils, injectors, compression, and vacuum are all within spec.

Do I need to replace the whole ignition coil pack for a single cylinder misfire?

If the vehicle uses individual coil‑on‑plug units, only the coil for cylinder 2 needs to be tested and replaced if faulty. Replacing the entire pack is unnecessary unless multiple coils are failing.

Will cleaning the fuel injector fix the code?

Cleaning can help if the injector is partially clogged, but if the injector is mechanically damaged or has an electrical fault, it will need to be replaced.

Is it safe to drive with a P0302 code?

Driving with a misfire can cause higher emissions, reduced fuel economy, and potential damage to the catalytic converter. It is best to diagnose and repair the issue promptly.