P0306: How to Diagnose & Fix — Cylinder 6 Misfire Detected
104 vehicles · 26 makes · $50-$25,000 repair
How to diagnose and fix P0306: most-reported vehicles
Ranked by owner reports. Each card gives the symptoms, how to confirm the cause, the fix, parts and sources for that vehicle.
Hyundai Sonata · 2011–2019
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.
Common Symptoms
- Knocking noise from engine
- Engine stalling
- Check engine light
- Loss of power
- Engine seizure
How to Fix
Check VIN for active recalls - Hyundai provides free engine replacement for affected vehicles. Install the knock sensor detection system (KSDS) software update that monitors for bearing wear. Change oil every 5,000 miles. If engine fails and under warranty, replacement is free. Out of warranty replacement: $4,000-8,000.
Owner tips & cautions
- TipDIY repairs can save significantly - dealer charges $4,000-8,000 but DIY costs are typically 50-70% less
- WarningThis is a high-severity issue - ignoring it can lead to costly repairs or safety concerns. Address it promptly.
- TipGet a proper diagnosis before replacing parts - similar symptoms can have different causes
Sources for this issue (1)
- NHTSA Recall 17V-224recall
Mazda MX-5 Miata · 1999–2005
The NB Miata (1999-2005) crankshaft position sensor (CPS) is a known failure point. The sensor deteriorates from engine heat, causing intermittent stalling, no-start conditions, and random misfires. Failure is often heat-related - the car runs fine when cold but stalls or dies after reaching operating temperature.
Common Symptoms
- Engine stalls when hot, restarts after cooling down
- Intermittent no-start condition (cranks but does not fire)
- Random misfires and rough running at operating temperature
- Check engine light with P0335 (CPS circuit) code
How to Fix
Replace crankshaft position sensor with OEM Mazda unit (N3A1-18-221A). Aftermarket sensors (Delphi, Dorman) have higher failure rates on this application. The sensor is located on the rear of the engine block near the flywheel.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Genuine Mazda BP4W-18-221B crankshaft position sensorOEMMazda BP4W-18-221B
Confirm VIN before ordering; thi
As an Amazon Associate, we earn from qualifying purchases; other part links may also earn au7o a commission. Confirm fitment by VIN before buying.
Owner tips & cautions
- TipCarry a spare CPS in the trunk - they fail without warning. Miata.net CPS mega-thread
- TipRoute sensor wiring away from exhaust manifold heat to extend sensor life
Hyundai Tucson · 2011–2019
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.
Common Symptoms
- Metallic knocking from engine
- Engine stalling without warning
- Check engine light with P1326 code
- Loss of power while driving
- Excessive oil consumption
How to Fix
Check VIN for active recalls at NHTSA.gov. Ensure the Knock Sensor Detection System (KSDS) software update has been installed - this monitors for early signs of bearing failure and can put the engine in limp mode. If engine has seized, Hyundai will replace it under recall. Out-of-warranty replacement runs $4,500-7,500. Use full synthetic 0W-20 oil and change every 5,000 miles.
Owner tips & cautions
- TipGet the KSDS software update immediately if not already done - it can detect bearing failure early and prevent catastrophic seizure
- WarningIf you hear any knocking noise, stop driving immediately. Continued driving can destroy the engine beyond repair
Sources for this issue (1)
Porsche 911 · 2009–2019
Honda Pilot · 2016–2022
Find P0306 by make
Browse every documented model and issue for your make.
P0306 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 P0306 mean?
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.
What are the most common causes of P0306?
The most common causes of P0306 are: 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. The specific cause varies by vehicle.
How much does it cost to fix P0306?
Repair costs for P0306 range from $50 to $25,000, depending on the vehicle and root cause.
Which vehicles are affected by P0306?
Au7o has documented P0306 across 104 vehicle models from 26 manufacturers: Acura, Audi, BMW, Cadillac, Chevrolet, Chrysler, Dodge, Ford, GMC, Genesis, Honda, Hyundai, Infiniti, Jaguar, Jeep, Kia, Lexus, Lincoln, Mazda, Nissan, Porsche, RAM, Saturn, Subaru, Toyota, Volkswagen.
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.