CodeXOBD

P0302 — Cylinder 2 Misfire Detected

P0302 means cylinder 2 is not firing correctly. Ignition components, fuel injectors, or compression problems specific to that cylinder are the causes to investigate.

High

The engine runs rough, vibrates, and has reduced power. A flashing check engine light indicates active misfires that can damage the catalytic converter. This code will cause an emissions test failure.

$10–$500Parts, typical range
0.3–3 hLabour
estimateNot a quote · 2026 basis

What P0302 means

The module monitors crankshaft speed fluctuations to detect misfires. When cylinder 2 contributes less power than expected, the speed drops slightly during that cylinder's firing event. P0302 sets when this pattern is detected consistently. A misfire means the air-fuel mixture in cylinder 2 did not burn — either because it did not ignite (ignition fault), did not get fuel (injector fault), or could not compress (mechanical fault).

Technical summary
SystemPowertrain — ignition and misfire
How a misfire is detectedThe crankshaft sensor gives position and speed, the camshaft sensor gives which stroke, and the module times the coil and injector for each cylinder from both. It detects a misfire by the small deceleration of the crankshaft that follows a cylinder which failed to fire, and attributes it to a cylinder when the pattern is consistent.Crank sensorposition, speedCam sensorwhich strokeModuletimes the sparkCoil & injectorper cylinderA misfire is measured as crankshaft deceleration, not as a missing spark

Symptoms you may notice

What causes P0302

Spark plug in cylinder 2 is fouled or worn

Very likelylow costeasy

A worn, fouled, or cracked spark plug cannot ignite the mixture. This is the cheapest and most common cause.

Ignition coil for cylinder 2 has failed

Likelylow costeasy

On coil-on-plug systems, the coil for cylinder 2 may have failed. Swap it with another cylinder — if the misfire follows the coil, the coil is the fault.

Fuel injector for cylinder 2 is clogged or failed

Possiblemedium costmoderate

A clogged or electrically failed injector does not deliver fuel to cylinder 2.

Low compression in cylinder 2

Rarehigh costhard

A leaking head gasket, worn piston rings, or burned valve reduces compression below the point where the mixture can ignite reliably. This is the most expensive cause.

How to diagnose it

1

Swap the ignition coil with another cylinder

Move the cylinder 2 coil to another cylinder and clear the codes. If the misfire moves to the new cylinder, the coil is bad.

Tools: Basic hand toolsIf it passes: Misfire stays on cylinder 2. Continue to step 2.If it fails: Misfire followed the coil — replace it.
2

Inspect the spark plug

Remove and inspect the cylinder 2 spark plug. Look for wear, fouling, oil deposits, or a cracked insulator.

Tools: Spark plug socket, Inspection lightIf it passes: Plug looks normal. Continue to step 3.If it fails: Replace the plug (and all others if near service interval).
3

Check compression in cylinder 2

Perform a compression test. Compare cylinder 2 against the others — it should be within 10% of the average.

Tools: Compression gaugeExpected: Within 10% of other cylindersIf it passes: Compression is normal. The injector is the remaining suspect.If it fails: Low compression — investigate valves, rings, or head gasket.

Related codes

P0300P0301P0303P0304

Common questions

Can I drive with a misfire on cylinder 2?

A steady misfire will damage the catalytic converter over time because unburned fuel reaches it. A flashing check engine light means active misfires — do not drive, stop as soon as it is safe.

Why swap the coil instead of replacing it?

Swapping is a diagnostic step, not a repair. If the misfire moves to the new cylinder, you know the coil is bad. If it stays, you have saved the cost of a coil you did not need.

Last verified 2026-07-27 · Sources: SAE J2012 — Diagnostic Trouble Code Definitions and Failure Type Byte (SAE International)

This information is for general guidance and is not a substitute for professional diagnosis. Cost figures are estimates, not quotes.