P0305 on Saturn: How to Diagnose & Fix
Cylinder 5 Misfire Detected
2 Saturn models · 2 documented issues · $150-$800 repair
P0305 on Saturn by model: symptoms, diagnosis and fix
The 3.6L V6 Auras are reported to throw misfire codes, frequently as a downstream symptom of the stretched timing chains but also from worn ignition coils/spark plugs. Owners experience rough idle, hesitation, and a check engine light. P0300 with cylinder-specific misfire codes is common.
Common Symptoms
- Check engine light (often flashing)
- Rough idle / shaking
- Hesitation or stumble on acceleration
- Reduced fuel economy
How to Fix
Diagnose root cause: inspect/measure timing chain deviation first (since chains are a known weak point), then replace spark plugs and any failed ignition coils. Address timing chains if correlation codes accompany the misfire.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Genuine GM spark plug 19300872 (replaces 12597464)
Confirm VIN/engine and current supersession before ordering.
- Genuine GM ignition coil 12632479
Confirm VIN/connector and current supersession.
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Sources for this issue (3)
On the 3.0L and 3.5L V6 Vue models, the valve cover gaskets become brittle and leak oil down into the spark plug tubes. The oil soaks the coil-on-plug boots, causing the rubber to swell and degrade so spark grounds out, producing misfires and rough running. Oil also drips onto the exhaust manifold, creating a burning-oil smell.
Common Symptoms
- Engine misfire
- Rough idle / poor performance
- Burning oil smell
- Oil in spark plug tubes
- Check engine light (misfire codes)
How to Fix
Replace the leaking valve cover gaskets and clean oil from the spark plug tubes, then replace the oil-soaked coil boots (and plugs if fouled). Replacing only the boots without fixing the valve cover gasket leak leads to repeat failure, so address the gasket as the root cause.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Beck/Arnley 036-1708 two-cover gasket and tube-seal set
Not the 2002-2003 3.0L, four-cylinder or 2008-2010 V6 branches; confirm engine/VIN and inspect covers for damage.
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Sources for this issue (4)
- Saturn Vue: Bad Coil Packs → Symptoms and Diagnosis | Drivetrain Resourcearticle
- Saturn Vue Ignition System Guide: Replacing Your Coil-on-Plug Boots (2002-2010) | Go-Partsarticle
- Engine Oil Leak From Valve Cover Gaskets: Saturn Vue | RepairPalarticle
- 2005 Saturn Vue CYL 3 misfire — oil in spark plug wells, valve cover gasket fix | ScannerDanner Forumforum
P0305 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 P0305 mean on a Saturn?
P0305 stands for "Cylinder 5 Misfire Detected." This code means the engine control module detected a misfire on cylinder number 5, meaning that cylinder is not burning its air-fuel mixture properly on some combustion cycles. The computer senses misfires by watching for tiny fluctuations in crankshaft speed each time a cylinder fails to fire correctly. A misfire wastes fuel, can make the engine run rough or shake, and dumps unburned fuel into the exhaust, which can overheat and damage the catalytic converter. It generally points to a problem with spark, fuel delivery, or compression specifically affecting cylinder 5. On Saturn it is documented across 2 models: Aura, Vue.
What are the most common causes of P0305?
The most common causes of P0305 are: Worn or fouled spark plug on cylinder 5, Failed ignition coil or coil pack for cylinder 5, Faulty or clogged fuel injector on cylinder 5, Vacuum or intake air leak affecting that cylinder, Bad spark plug wire or boot (on applicable engines), Low compression from worn rings, valves, or head gasket, Carbon buildup or sticking valve on cylinder 5, Lean or rich fuel condition affecting the cylinder. The specific cause varies by vehicle.
How much does it cost to fix P0305 on a Saturn?
Published repair estimates on Saturn range from $150 to $800 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.
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Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.