P0303 on Hyundai Sonata
Cylinder 3 Misfire Detected
Methodology: Reviewed against the SAE J2012 generic DTC definition and NHTSA owner-complaint patterns, then scoped to Hyundai Sonata context without treating complaints as confirmed diagnoses.
Sources: SAE/OBD-II definitions, manufacturer service information, and public reliability reports (including NHTSA where applicable).
- SAE J2012 Diagnostic Trouble Code Definitions — Generic diagnostic trouble code definition reference for P0303.
- NHTSA recalls, complaints, and manufacturer communications — Used to check public owner complaint context, recall status, and safety-related manufacturer communications by VIN or vehicle.
Limits: Guidance is informational and may not match every model-year or revision. Confirm with the official manual and diagnostics before replacing parts. For safety-critical or electrical work, use a qualified technician.
What P0303 Means on Your Hyundai Sonata
P0303 is a diagnostic trouble code indicating: Cylinder 3 Misfire Detected. This code relates to the ignition system system. The vehicle's computer detected a condition outside normal operating parameters and stored this code.
Real Hyundai Sonata Owner Reports
Source: NHTSA Complaints Database
"Our 2015 Sonata has experiencing Engine failure several times due to excessive and irregular oil consumption."
"Vehicle has been repaired due to broken valve. Vehicle was unsafe to drive. Valve burnt at 70 mph. Car threw misfire code P0303 and started shaking. This issue could have caused an accident. Valves were replaced at Young Hyundai in Ogden Utah."
"I changed out every cylinder, axel, within 6 months and now on March 22, 2023, they said I needed a new engine. P0300, P0303 MISFIRE. They said the car misfired. I thought that's why they changed all the cylinders. WHY DID THIS HAPPEN? My car has been parked in the garage."
All reports filed by vehicle owners directly with the U.S. Department of Transportation.
📊 Complaint Trend by Model Year
Common Causes on Hyundai Sonata
Based on NHTSA complaint component analysis for this vehicle.
What To Do Next
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1
Check for recalls on YOUR VIN
Go to nhtsa.gov/recalls and enter your VIN. If your vehicle is covered, repairs are free.
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2
Get a proper diagnosis
A code alone doesn't tell you the exact failed part. A diagnostic at a shop ($50–$150) pinpoints the root cause before you spend money on parts.
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3
Compare repair quotes
Get 2–3 quotes. Dealer vs. independent shop prices often differ 30–50% for the same repair.