As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PILOT REPORTED LEFT ENGINE FIRE CASS MESSAGE IN FLIGHT. THE PROPELLER WAS FEATHERS & ENGINE WAS SHUT DOWN AS A PRECAUTION. MAINTENANCE INSPECTED AND FOUND NO DAMAGE. THE LT ENGINE #2 FIRE DETECTOR WAS DETERMINED TO BE FAULTY. DETECTOR WAS REPLACED WITH NO FURTHER DEFECTS NOTED.