P0306 on a Toyota: 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 Toyota

On a Toyota, P0306 means the engine computer detected that cylinder 6 is misfiring, so that cylinder is not producing power on schedule. Because each cylinder on a Toyota V6 has its own ignition coil and spark plug, the fault usually points to cylinder 6's own parts rather than a shared fuel or air system. A flashing light means the misfire is severe enough to risk damaging the catalytic converter.

Is P0306 common on Toyotas?

P0306 shows up on Toyota V6 models like the Camry, Avalon, and Highlander, usually at higher mileage. Worn spark plugs and failing coil-on-plug ignition coils on the 3.5L V6 are the typical culprits. A clogged fuel injector or low compression in cylinder 6 is less common but possible.

Commonly reported on: Camry, Avalon, Highlander, Sienna.

Symptoms

Check engine light on (flashing if severe)
Rough idle or shaking at idle
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