What was found
APU HAS HISTORY OF AUTO SHUT DOWN. GROUNDED - YES. MULTIPLE MAINT MESSAGES SPEED SENSOR 1 SHOWS CIRCUIT FAILURE / SPEED SENSOR 1 SHOWS OPEN CIRCUIT. REF FIM 49-30 TASK 802. NO FOD NOTICED IN INLET OR PLENUM. PERFORMED WIRE HARNESS INSP NO DEFECTS NOTED. PERFORMED CONTINUITY CHECK OF P12 / SPEED SENSOR TO APU FIRE WALL CONNECTOR CONTINUITY CHECKS GOOD. REMOVED AND REPLACED SPEED SENSOR REF B737-900 AMM TASK 49-61-21. OPS CHECK GOOD, LEAK CHECK GOOD. NO FURTHER DEFECTS NOTED.