What was found
FLIGHT 3117 - BUF-LGA - EN ROUTE FROM BUF TO LGA, ENCOUNTERED EICAS MESSAGE E2 FIRE DET FAIL. PERFORMED QRH CHECKLIST FOR MESSAGE. THERE WAS NO ENGINE FAILURE ASSOCIATED WITH THE MESSAGE. DID NOT SUSPECT FIRE OR OVERHEAT AS ALL ENGINE AND OTHER SYSTEM INDICATIONS WERE NORMAL AND NO FIRE WARNING WAS DISPLAYED. ELECTED TO DO A PRECAUTIONARY ENGINE SHUTDOWN. CONDUCTED ENGINE SHUTDOWN AND DIVERTED TO SYR AND DECLARED AN EMERGENCY. MAINTENANCE REMOVED AND REPLACED THE ENGINE NR 2 FIRE LOOP.