As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
IN CRUISE AT FL 370 MASTER CAUTION - OVERHEAT/DET ILLUMINATED AND APU DET INOPERATIVE ILLUMINATED. ACFT GROUNDED. TSR ISSUED. PERFORMED FIM 26-10, TASK 801. NO FAULTS FOUND IAW TSR STEP 3: REPLACED APU TAIL PIPE DETECTOR REF 26-15-01-000-802. PERFORMED APU DETECTOR SYS TEST SYS CKS NORMAL.