As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SEA - FLIGHT CREW REPORTED A MASTER FIRE WARNING INDICATION IN CONJUNCTION WITH A B-LOOP DETECTOR FAULT DURING CLIMBOUT. INDICATION LASTED 20 SECONDS. INSPECTED ENGINE AREA, NO DEFECTS NOTED. PLACED B-LOOP DETECTION CIRCUIT ON DEFERRED MAINTENANCE LIST. OPERATIONAL CHECKS GOOD. AIRCRAFT RETURNED TO SERVICE.