What was found
CRUISE FLIGHT, AT FL410, A WHITE CAS MESSAGE OF " L ENG FIRE FAIL" INDICATING FIRE DETECTION SYS DETECTED A FAULT. APPROX 30 SECONDS LATER, ALERTED WITH AN AUDIO ALERT OF "LT ENGINE FIRE" & ASSOCIATED "FIRE" INDICATED IN ITT GUAGE, & A MASTER WARNING & TRIPLE-CHIME WITH FLASHING LIGHT. NO OTHER ABNORMAL INDICATIONS FROM LT ENGINE. IMMEDIATELY REDUCED LT ENGINE TO IDLE THRUST & FOLLOWED "ENGINE FIRE" CHECKLIST. FIRE INDICATION DID NOT CLEAR, CONTINUED TO SHUT ENGINE DOWN & SELECTED LT "FIRE PUSH" SWITCH & NR 1 LT ENGINE FIRE EXTINGUISHER CARTRIDGE ACTIVATED. DID NOT CLEAR FIRE WARNING, DECLARED AN EMERGENCY & REQUESTED VECTORS TO A NEARBY SUITABLE FIELD. DURING DESCENT, CONTINUED WITH MFG ENGINE FIRE CHECKLIST, ENGINE SHUTDOWN IN FLIGHT CHECKLIST, & SINGLE ENGINE LANDING CHECKLIST. ACTIVATED LT ENGINE NR 2 FIRE EXTINGUISHER CARTRIDGE IAW CHECKLIST, DID NOT CLEAR FIRE WARNING. AN UNEVENTFUL LANDING ACCOMPLISHED. TROUBLESHOOTING REVEALED ENGINE FIREWALL SENSING ELEMENT HAD BEEN KINKED & SHORTED. SENSING ELEMENT, & ENGINE FIRE EXTINGUISHERS REPLACED, SYS OPS CHECKED GOOD AND AIRCRAFT RETURNED TO SERVICE.