P0306 on Hyundai
Cylinder 6 Misfire Detected
P0306 on Hyundai vehicles indicates cylinder 6 misfire detected. Au7o has documented this code across 3 Hyundai models — most commonly on Elantra, Sonata, Tucson. This code means the engine computer detected a misfire on cylinder 6 — that cylinder isn't burning its fuel-air mixture properly. The computer senses misfires by watching for tiny variations in crankshaft speed each time a cylinder should fire, and when cylinder 6 repeatedly fails to contribute, this code sets. You may feel a shake or stumble, especially at idle or under load, along with reduced power and possibly a flashing check-engine light, which signals a misfire severe enough to damage the catalytic converter. A misfire comes down to a problem with spark, fuel, or compression in that cylinder. Typical repair costs on Hyundai range from $4,000 to $8,000, depending on the specific model and root cause.
Common Causes of P0306
- •Worn or fouled spark plug on cylinder 6
- •Failed ignition coil for cylinder 6
- •Clogged, leaking, or failed fuel injector
- •Vacuum or intake air leak affecting that cylinder
- •Low compression (worn rings, burnt valve, head gasket)
- •Damaged plug wire or coil connector
- •Carbon buildup or worn valvetrain components
P0306 on Hyundai by Model
Hyundai Elantra(1 issue)
- Nu Engine Bearing Failure and Seizure2011-2016
The 1.8L Nu engine in 2011-2016 Elantras is prone to premature failure due to manufacturing defects including piston ring issues, connecting rod bearing failure, and oil passage problems. Metal debris from failed components can circulate through the engine causing catastrophic damage. A class action settlement covered these vehicles with extended warranty up to 140,000 miles.
Hyundai Sonata(1 issue)
- Theta II Engine Seizure/Failure2011-2019
The Theta II engine can seize due to metal debris blocking oil flow to connecting rod bearings. Hyundai issued recalls and extended warranties. Affected engines may need replacement.
Hyundai Tucson(1 issue)
- Theta II Engine Seizure Due to Connecting Rod Bearing Failure2011-2019
The Theta II GDI engine in 2011-2019 Tucson models is susceptible to connecting rod bearing failure caused by manufacturing debris restricting oil flow. This can lead to catastrophic engine seizure, often without warning. Hyundai issued multiple recalls (19V-601, 20V-150) and extended the engine warranty to 15 years/unlimited miles for original owners.
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View P0306 across all makes →Frequently Asked Questions
What does P0306 mean on Hyundai?▼
P0306 stands for "Cylinder 6 Misfire Detected." This code means the engine computer detected a misfire on cylinder 6 — that cylinder isn't burning its fuel-air mixture properly. The computer senses misfires by watching for tiny variations in crankshaft speed each time a cylinder should fire, and when cylinder 6 repeatedly fails to contribute, this code sets. You may feel a shake or stumble, especially at idle or under load, along with reduced power and possibly a flashing check-engine light, which signals a misfire severe enough to damage the catalytic converter. A misfire comes down to a problem with spark, fuel, or compression in that cylinder. On Hyundai specifically, this code is documented across 3 models.
What causes P0306 on Hyundai vehicles?▼
Common causes on Hyundai: Worn or fouled spark plug on cylinder 6, Failed ignition coil for cylinder 6, Clogged, leaking, or failed fuel injector, Vacuum or intake air leak affecting that cylinder, Low compression (worn rings, burnt valve, head gasket). Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0306 on a Hyundai?▼
Repair costs on Hyundai range from $4,000 to $8,000, depending on the specific model and root cause.
Which Hyundai models have P0306 documented?▼
Au7o has documented P0306 on 3 Hyundai models: Elantra, Sonata, Tucson.