What was found
L BLEED AIR MESSAGE ILLUMINATED IN FLIGHT AS DIRECTED BY THE CHECKLIST THE LT ENGINE WAS SHUTDOWN BY CREW BECAUSE THE MESSAGE REMAINED ON AFTER X-LIST ITEMS WERE COMPLETED SIDE NOTE ENGINE EVENT BUTTONS WERE PRESSED ABOUT 45 SECONDS AFTER MESSAGE ILLUMINATED. T/S GAINED ACCESS TO LEFT BLEED AIR DUCTING. NO DEFECTS NOTED. RANG OUT FIRELOOP & CONTROL BOXES. NO DEFECTS NOTED. PER GAC TECH REP SWAPPED CONTROL BOXES. RAN ACFT AT T/O POWER. NO DEFECTS NOTED PER TECH OPS. REMOVED AND REPLACED THE LEFT BLEED LEAK DETECT LOOP AND THE CONTROL BOX WITH A NEW LOOP AND NEW BOX. RAN ACFT. OPS CHECK GOOD I/A/W G-200 M/M 21-61-00. REINSTALLED ACCESS ITEMS.