P0306 on a BMW: 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 BMW

On a BMW, P0306 means the engine computer detected that cylinder 6 is misfiring, so that cylinder is not firing and producing power on schedule. BMW's inline-6 engines are known for this code because coil packs and spark plugs wear out with mileage, and cylinder 6 sits at the back of the engine. A flashing light means the misfire is severe enough to risk catalytic converter damage.

Is P0306 common on BMWs?

P0306 is common on BMW inline-6 models like the 3 Series, 5 Series, and X3 as the coil packs and plugs age. The N52, N54, and N55 engines all use individual coil packs that fail over time, and the rear cylinder is the one most often affected. Fuel injector issues on turbocharged models and low compression are less common causes.

Commonly reported on: 3 Series, 5 Series, X3, X5.

Symptoms

Check engine light on (flashing if severe)
Rough idle or shaking while idling
Loss of power or hesitation under load
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: Vacuum leak from a cracked intake boot
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	$90–350
Replace worn spark plugs	Yes	$80–300
Replace or clean the cylinder 6 fuel injector	Mechanic	$200–500
Run a compression test to rule out internal engine wear	Mechanic	$100–250

Frequently asked questions

Is it safe to drive my BMW with a P0306 code?

Only if the light is steady and the car runs fine. A flashing light means a severe misfire, so stop and have it towed.

Why is P0306 so common on BMW inline-6 engines?

The coil packs and spark plugs wear out with mileage, and the rear cylinder's coil gets the hardest life. Swapping coils between cylinders is a fast way to confirm it.

How much does it cost to fix P0306 on a BMW?

Coil and plug fixes usually run $90–$350. Injectors on turbo engines cost more, and engine repairs cost the most.