As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLT 1850 - SEA-FWA - DURING CRUISE, THE NR 3 ENGINE FIRE DETECTION LOOP ILLUMINATED. AIRCRAFT MADE AN UNEVENTFUL LANDING AT FWA. REPOSITIONED NR 3 ENGINE FIRE DETECTION LOOP. OPERATIONALLY CHECKED SYSTEM GOOD. THE AIRCRAFT WAS RETURNED TO SERVICE.