As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER TAXI OUT, THE NR 2 FIRE WARNING LIGHT CAME ON AND TWO FIRE BOTTLES WERE DISCHARGED. LIGHT REMAINED ON, PASSENGERS EVACUATED BY SLIDES. FOUND FIRE LOOP M337 HAS A SHORT BETWEEN PINS 4 AND 6 IN CONNECTOR D992. REPLACED LOOP SYSTEM, OPS CHECKS OK.