OBD codes / P0304
P0304
SeriousCylinder 4 Misfire Detected
Address promptly — can worsen or affect drivability.
Likely causes
- bad plug/coil cyl 4
- injector
- low compression
Common fixes
- swap coil to confirm
- replace plug
Seeing P0304 on your car? Get a diagnosis specific to your exact year, make and model.
Diagnose P0304 for my vehicleGeneric OBD-II reference. Manufacturer-specific behavior varies — confirm with a scan tool and, for safety-related codes, a professional inspection.