P0300 on a Volvo: 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 P0300 means on a Volvo

On a Volvo, P0300 means the engine computer sees misfires jumping between cylinders instead of on one fixed cylinder. A misfire means a cylinder is not burning its fuel properly, which wastes gas and can damage the catalytic converter if left alone.

Is P0300 common on Volvos?

P0300 is common on Volvo 5-cylinder engines like the 2.4L and 2.5T in the S60, V70, and XC70. Failing ignition coils are a well-known issue on these engines, and worn spark plugs are another top cause. A clogged PCV system and vacuum leaks can also cause random misfires.

Commonly reported on: S60, V70, XC70, XC90.

Symptoms

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

Common causes

most common: Failing ignition coils
common: Worn or fouled spark plugs
common: Clogged PCV system
less common: Vacuum leak
less common: Low compression from engine wear

How to fix it

Fix	DIY?	Typical cost
Replace failing ignition coils	Yes	$120–350
Replace worn spark plugs	Yes	$80–200
Replace the PCV oil trap and hoses	Mechanic	$200–500
Find and repair vacuum leaks	Yes	$10–100