As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APU OVERSPEED LIGHT ILLUMINATED IN FLIGHT, APU SHUTDOWN. GROUNDED - YES. AIR TURNBACK - DIVERSION TIME 33 MINUTES. PERFORMED APU BITE REF FIM 49-60 TASK 801 AND FOUND CODE 49-31014 APU OVERSPEED. PERFORMED FIM 49-30 TASK 802 ENGINE WIRE INSPECTION AND INLET INSPECTION WITH NO DEFECTS NOTED. REMOVED AND REPLACED APU FCU IAW AMM 49-31-11, OPS AND LEAK CHK NORMAL.