What was found
EICAS MSG: LT ENGINE BLEED OFF. REMOVED AND REPLACED LEFT ENGINE PRV CONTROLLER, IAW AMM 36-11-19. DRY MOTORED ENGINE AND FOUND NO LEAKS. PERFORMED ENGINE RUN, IAW AMM 71-00-00, OPERATIONS NORMAL. OBSERVED NORMAL DUCT PRESSURE. DUCT PRESSURE REMAINED STEADY THROUGH FULL PNEUMATIC LOAD. S/N OFF: 900350, P/N OFF: 792755-16. REMOVED AND REPLACED PRV, IAW AMM 36-11-10, NO LEAKS NOTED. OPERATIONS CHECK GOOD.