As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
L/H Engine Fire Warning Indication Sytem illuminated during take off hold position. Crew discharged both engine fire bottles and returned to gate.Maintenance trouble shot fire warning system and found a small chafe on FWD Fire Wire. Removed and replaced FWD Fire Wire and Fire Bottles. Aircraft returned to service.