P0306 Code: Cylinder 6 Misfire Detected

🟠 Moderate severity · drivable

Short drives with a steady light are generally okay, but fix it soon — and pull over right away if the light flashes.

What P0306 means

Cylinder 6 is misfiring, which means it isn't firing and producing power on schedule. As a single-cylinder code, P0306 localizes the fault to cylinder 6's own ignition and fuel components — its spark plug, coil, or injector — instead of the shared fuel/air systems that a random misfire (P0300) would implicate.

Symptoms

Check engine light on (flashing if severe)
Rough or vibrating idle
Hesitation and loss of power
Worse fuel economy

Common causes

most common: Worn or fouled spark plug on cylinder 6
common: Failing ignition coil or plug wire for cylinder 6
common: Clogged or leaking fuel injector on cylinder 6
less common: Low compression in cylinder 6 (rings, valve, or gasket)

How to fix it

Fix	DIY?	Typical cost
Swap cylinder 6's spark plug and coil with another cylinder to see whether the misfire follows them	Yes	$0–20
Replace the cylinder 6 spark plug	Yes	$10–50
Replace the cylinder 6 ignition coil	Yes	$50–200
Run a compression test on cylinder 6	Mechanic	$100–200

Frequently asked questions

Is P0306 confined to cylinder 6?

Yes. A single-cylinder misfire points to that cylinder's spark plug, coil, or injector. If the misfire skips between cylinders, the code is usually P0300.

What's the first thing to try for P0306?

The free swap test: move cylinder 6's plug and coil to another cylinder and re-scan. If the code moves, the swapped part is bad. If it stays, check the injector and compression.

How serious is a P0306?

Moderate. Drive briefly with a steady light, but a misfire sends unburned fuel into the catalytic converter, and a flashing light calls for stopping and towing.