The P0304 code in your 2019 Hyundai Sonata indicates the engine management system has detected persistent misfires in cylinder 4. As the final year of the seventh-generation Sonata, this midsize sedan's well-understood platform benefits from established diagnostic procedures and readily available service information.
Understanding P0304 in the 2019 Sonata
The 2019 Sonata offers the 2.4L four-cylinder as standard with a 2.0L turbocharged option. Both inline-four engines position cylinder 4 at the rear. The mature platform has well-documented maintenance requirements and common failure patterns, simplifying diagnosis on vehicles with potentially significant accumulated mileage.
Age-Related Considerations
Vehicles from 2019 may be approaching or past spark plug replacement intervals. Ignition coils degrade from years of heat cycling. The 2.4L and 2.0T engines have different wear patterns—the turbo experiences higher stress under boost. Review maintenance history when diagnosing misfires.
Diagnostic Process
Identify your engine type and review available maintenance records. Retrieve all codes noting vehicle mileage. Inspect spark plug condition—if original or maintenance is unknown, replacement is advisable. Test ignition coil output. Verify fuel injector operation. Consider the vehicle's age in your assessment.
Repair Recommendations
Replace spark plugs with Hyundai-approved components for your engine. Test and replace degraded ignition coils. Address fuel system concerns. Consider comprehensive ignition service if maintenance history is incomplete.