P0304 on KIA OPTIMA
What P0304 Means on Your KIA OPTIMA
Real KIA OPTIMA Owner Reports (Source: NHTSA Complaints Database)
"On Sunday, September 21st, 2025, my 2013 Kia Optima EX suffered sudden catastrophic engine failure while driving on the highway. The check engine light was flashing, the car misfired badly, lost complete power, and became unsafe to operate. The vehicle was then towed to Wagner Kia of Shrewsbury, MA."
"My 2016 Kia Optima is experiencing severe internal engine oil consumption that matches known issues Kia has recalled and extended warranties for. The vehicle loses 1–3 quarts of oil every few days with no external leaks."
"Excessive oil consumption started at 61,000 miles, causing engine misfires and dangerous power loss on the road. Engine codes 1326 and P0304 were frequent. Despite numerous services, including sensor replacements, spark plugs and oil top-offs, the problem worsened."
"The contact owns a 2020 Kia Optima. The contact stated that while her husband was driving at an undisclosed speed, the vehicle was shuddering. The contact's husband was able to drive to the residence."
Data from NHTSA Vehicle Complaints Database. All reports are filed by vehicle owners directly with the U.S. Department of Transportation.
Common Causes of P0304 on KIA OPTIMA
Percentages based on NHTSA complaint component analysis for this vehicle.
Complaint Trend by Year
What To Do Next
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1
Check for recalls on YOUR VIN
Go to nhtsa.gov/recalls and enter your VIN. Free repairs if your vehicle is covered.
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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.