P0305 on a Mercedes-Benz: 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 P0305 means on a Mercedes-Benz

On a Mercedes, P0305 means the engine computer detected a misfire on cylinder 5. That cylinder is not firing cleanly, which wastes fuel and can damage the catalytic converter if left alone. Because the code names one cylinder, the cause is usually its ignition coil, spark plug, or injector.

Is P0305 common on Mercedes-Benzs?

P0305 appears on Mercedes V6 and V8 models like the C-Class, E-Class, and S-Class. Failing ignition coils are a common cause on these engines, and worn spark plugs are another usual trigger at higher mileage. Fuel injector issues can also misfire a single cylinder.

Commonly reported on: C-Class, E-Class, S-Class, GLE.

Symptoms

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

Common causes

most common: Failing ignition coil on cylinder 5
common: Worn or fouled spark plug on cylinder 5
less common: Clogged or leaking fuel injector
less common: Wiring or connector issue at the coil
less common: Low compression from engine wear

How to fix it

Fix	DIY?	Typical cost
Replace the ignition coil on cylinder 5	Yes	$90–300
Replace the spark plug on cylinder 5 (or all plugs)	Yes	$60–200
Replace or clean the cylinder 5 injector	Mechanic	$250–650
Run a compression test if the misfire returns	Mechanic	$100–200

Frequently asked questions

Which Mercedes have a cylinder 5?

V6 and V8 models like the C-Class, E-Class, and S-Class. Four-cylinder models set P0301–P0304 instead.

What usually causes P0305 on a Mercedes?

A failing ignition coil is the most common cause, with worn spark plugs next. A leaking injector can also misfire one cylinder on higher-mileage engines.

Is it safe to drive my Mercedes with P0305?

A steady light is usually okay for short trips. A flashing light means a severe misfire, so stop and get it towed.