P0301 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 P0301 means on a BMW

On a BMW, P0301 means the engine computer has detected that cylinder 1 is not firing properly and is failing to contribute its share of power. Because the code points to one cylinder, the fault is usually specific to cylinder 1, such as its spark plug, ignition coil, or fuel injector.

Is P0301 common on BMWs?

P0301 is common on BMW inline-6 engines, especially the turbocharged N54 and N55 in the 3 Series and 5 Series, where ignition coils fail frequently. Spark plugs and fuel injectors are other common causes on these engines. Many BMW owners replace all the coils at once because a second coil usually fails soon after the first.

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

Symptoms

Check engine light on (flashing if severe)
Rough idle or shaking at a stop
Loss of power or hesitation under acceleration
Poor fuel economy

Common causes

most common: Failing ignition coil for cylinder 1
common: Worn spark plug in cylinder 1
common: Clogged or leaking fuel injector in cylinder 1
less common: Vacuum leak near the intake
less common: Low compression in cylinder 1 from engine wear

How to fix it

Fix	DIY?	Typical cost
Replace the ignition coil for cylinder 1	Yes	$100–300
Replace the spark plug in cylinder 1	Yes	$40–150
Replace the fuel injector in cylinder 1	Mechanic	$300–900
Run a compression test to rule out internal engine wear	Mechanic	$100–250