As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CREW RECEIVED A FIRE WARNING INDICATION FOR THE LT ENGINE. THERE WERE NO INDICATIONS OF AN ENGINE FIRE. THE FLIGHT RETURNED TO THE GATE NORMALLY AND PASSENGERS DEPLANED NORMALLY. THE LEFT HAND FIRE TEST SWITCH TO BE STICKING AND WAS REPLACED. A SATISFACTORY OPERATIONAL CHECK WAS PERFORMED AND AIRCRAFT RETURNED TO SERVICES.