As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE WAITING TO TAKEOFF, LT ENGINE GOT MASTER CAUTION AND A FIRE WARNING CREW FOLLOWED EMERGENCY CHECKLIST AND SHUTDOWN ENGINE AND FIRED EXTINGISHER PAX WERE DEPLANNED AIRCRAFT RETURNED TO GATE WITH NO FURTHER INCIDENT. REPLACED LOOP P/N 244-12886.