What was found
FLIGHT DIVERTER INTO OAK DUE TO A ENG LOW PRESSURE LIGHT ILLUMINATED. A-SYSTEM WAS DECREASING RAPIDLY. LDG GEAR SELECTOR MOVED TO OFF. A-SYS QUANTITY STABILIZED JUST UNDER 1/4 TANK. INSPECTED AND FOUND LEFT MLG ACTUATOR DRAIN PLUG NOT SAFETIED. RETORQUED AND RESAFETIED DRAIN PLUG. REMOVED AND REPLACED A-SYS CASE DRAIN FILTERS. LEAKS CHECK GOOD PER BOEING MM. REPOSITIONED SENSOR AT LEFT A/C DUCT, OPS CHECKS OK PER BOEING MM.