P0306 on a Hyundai: Causes, Fixes & Repair Cost

🟠 Moderate severity · drivable

If the check engine light is flashing, stop driving — a severe misfire can damage the catalytic converter. A steady light is usually safe for a short drive to a shop.

What P0306 means on a Hyundai

On a Hyundai, P0306 means the engine computer detected that cylinder 6 is misfiring, so that cylinder is not producing power on schedule. It appears on Hyundai V6 models like the Genesis, Azera, and Santa Fe, which use one ignition coil per cylinder. A flashing light means the misfire is severe enough to risk catalytic converter damage.

Is P0306 common on Hyundais?

P0306 shows up on Hyundai V6 models as the Lambda-series engine accumulates miles, most often on the Genesis, Azera, and Santa Fe. Ignition coils and spark plugs are the usual wear items. Clogged fuel injectors and low compression from engine wear are less common causes.

Commonly reported on: Genesis, Azera, Santa Fe, Sonata.

Symptoms

Check engine light on (flashing if severe)
Rough idle or shaking while idling
Loss of power or hesitation when accelerating
Poor fuel economy

Common causes

most common: Failing ignition coil on cylinder 6
common: Worn or fouled spark plug in cylinder 6
common: Clogged or leaking fuel injector on cylinder 6
less common: Damaged wiring or connector at the cylinder 6 coil
rare: Low compression in cylinder 6 from engine wear

How to fix it

Fix	DIY?	Typical cost
Replace the ignition coil on cylinder 6	Yes	$80–350
Replace worn spark plugs	Yes	$60–250
Replace or clean the cylinder 6 fuel injector	Mechanic	$150–400
Run a compression test to rule out internal engine wear	Mechanic	$100–200