As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FAULT LIGHT ILLUMINATED ON APU CSS AT FL380. GROUNDED - YES. CHECKED MAG PLUG PER FIM 49-60 TASK 817 STEP 4. NO DEFECTS NOTED. REPLACED SPEED SENSOR PER FIM 49-60 TASK 817 STEP 8 AND AMM 49-61-21. OPS CK GOOD, LK CK GOOD. NO FAULTS FOUND. STARTED APU SEVERAL TIMES WITH NO DEFECTS NOTED. ETOPS GROUND VERIFICATION C/W. THIS CLEARS MEL 49-1B.