What was found
PHX - ATB - FLT 675 - DURING CLIMB, THE CREW RECEIVED A NR 2 ENGINE FIRE WARNING. ENGINE INDICATIONS WERE NORMAL. THE CREW WAS AWARE OF THE HISTORY FOR THIS INDICATION AND DID NOT INITIATE AN IFSD. CREW RETURNED TO PHX. CRITICAL ALERT - 9505723 WAS INITIATED TO REPLACE LOOPS A & B FOR ENGINE 2 FAN, CORE AND PYLON SENSORS. PERFORM SHAKEDOWN OF WIRING AND CONNECTORS WHILE MONITORING RESISTANCE AT FIRE DETECTION UNIT 2, 2WD2/A-K AND L FOR LOOP A. ALSO LOOP B 2WD2/B - K & L. SEE ASM 26-12-00. PERFORM INSTALLATION TESTING AND RESTORE A/C TO NORMAL. MAINTENANCE FOUND NR 2 ENG CORE FIRE LOOP "B" WIRE HAS AN OPEN APPROXIMATELY 4 INCHES BACK FROM THE CONNECTOR. REMOVED BAD WIRE AND RE-TERMINATED CORE FIRE LOOP