P0304 on a Volvo: Causes, Fixes & Repair Cost

🟠 Moderate severity · drivable

A steady light usually means you can drive a short distance, but a flashing light means the misfire is severe — pull over and get the Volvo towed.

What P0304 means on a Volvo

On a Volvo, P0304 means the engine computer found that cylinder 4 is misfiring — it is not burning fuel on schedule. The code points at one cylinder, so the fault is almost always that cylinder's own spark plug, ignition coil, or fuel injector. Volvo's four-cylinder Drive-E engines and older five-cylinders use coil-on-plug ignition.

Is P0304 common on Volvos?

P0304 shows up on Volvos like the XC60, XC90, and S60, often at higher mileage. Ignition coils and spark plugs are the usual suspects, and coil failures are a common wear item on turbocharged Volvo engines. A failing fuel injector is less common but possible.

Commonly reported on: XC60, XC90, S60, S90.

Symptoms

Check engine light on, flashing if the misfire is severe
Rough idle or shaking while stopped
Loss of power or hesitation when accelerating
Worse fuel economy

Common causes

most common: Worn or fouled spark plug in cylinder 4
common: Failing ignition coil for cylinder 4
less common: Clogged or leaking fuel injector on cylinder 4
less common: Vacuum or intake air leak near cylinder 4

How to fix it

Fix	DIY?	Typical cost
Replace the spark plugs	Yes	$100–250
Replace the cylinder 4 ignition coil	Yes	$80–220
Swap the coil with another cylinder to confirm the fault first	Yes	$10–30
Replace the fuel injector on cylinder 4	Mechanic	$300–700