As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LAS - INFLIGHT LAX ORD NUMBER TWO ENGINE FIRE WARNING LOOP-B WHILE LOOP-A ON PLACARD. AIRCRAFT DIVERTED TO LAS AND LANDED WITHOUT INCIDENT. NO OTHER INDICATIONS OF FIRE. NO FIRE WAS CONFIRMED UPON LANDING. REPLACED LOWER FIRE DETECTION UNIT ON RIGHT HAND ENGINE. SYSTEM GROUND CHECKED NORMAL OPERATION.