P0303 on Volvo: How to Diagnose & Fix
Cylinder 3 Misfire Detected
1 Volvo model · 1 documented issue · $100-$500 repair
P0303 on Volvo by model: symptoms, diagnosis and fix
Nearly 20% of C30 owners report rough idle issues according to Consumer Reports data. The rough idle can be caused by several factors: failing ignition coils, ETM (Electronic Throttle Module) issues, PCV system failures, and vacuum leaks. The 2.5L turbo I5 is particularly sensitive to PCV system degradation which causes positive crankcase pressure and oil ingestion into the intake. The 2.0L I4 models are less affected but can develop similar idle issues from ignition coil failures.
Common Symptoms
- Rough or uneven idle
- Engine hesitation on light throttle
- Intermittent misfires at idle
- Engine vibration felt through steering wheel at idle
- Slight RPM fluctuation at idle
How to Fix
Start diagnostics with the PCV system — check the PCV valve and breather hose for blockage or collapse. Replace ignition coils and spark plugs if misfires are present. Clean the electronic throttle body. Check for vacuum leaks using a smoke test. The PCV system on the 2.5L turbo requires periodic replacement of the breather box/oil trap assembly ($50-$150 for parts).
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- CRP 202171 Volvo RNC five-cylinder PCV diaphragm
replace a confirmed torn oil-filter-housing PCV diaphragm causing abnormal crankcase vacuum and idle symptoms Fitment/availability: Applicable 2008-2013 Volvo C30 late-RNC turbo five-cylinder oil-filter-housing diaphragm branch; confirm …
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Owner tips & cautions
- TipCheck the PCV breather box first — it's the #1 cause of rough idle on the 2.5T engine and is a cheap fix.
- TipReplace all ignition coils at once rather than chasing individual failures — they tend to fail in sequence.
Sources for this issue (1)
P0303 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0303 mean on a Volvo?
P0303 stands for "Cylinder 3 Misfire Detected." This code means your engine's computer detected a misfire specifically in cylinder number 3 — that cylinder isn't burning its fuel-air mixture properly or completely. The computer senses misfires by watching for tiny fluctuations in crankshaft speed each time a cylinder is supposed to fire. A misfire wastes fuel, can cause a noticeable shake, rough idle or loss of power, and can flood raw fuel into the exhaust where it may overheat and damage the catalytic converter. Because the fault is isolated to one cylinder, the cause is usually something specific to that cylinder's ignition, fuel delivery, or compression. On Volvo it is documented across 1 model: C30.
What are the most common causes of P0303?
The most common causes of P0303 are: Worn or fouled spark plug in cylinder 3, Failed or weak ignition coil on cylinder 3, Bad spark plug wire or boot (where applicable), Clogged or leaking fuel injector for cylinder 3, Vacuum or intake air leak affecting that cylinder, Low compression (worn rings, burnt/leaking valve, head gasket), Wiring or connector fault at the coil or injector. The specific cause varies by vehicle.
How much does it cost to fix P0303 on a Volvo?
Published repair estimates on Volvo range from $100 to $500 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
Looking for P0303 on a different make?
View P0303 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.