As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
IAW MAINTENANCE REQUEST, TRIED CSS. 1ST ATTEMPT AT FL 380. GOT FAULT LIGHT. OUT AFTER 3+ MINUTES. 2ND ATTEMPT AT FL 365. FAULT LIGHT AGAIN, LIGHT OUT AFTER ABOUT 5.5 MINUTES. ACFT GROUNDED. PERFORMED APU BITE TEST REF AMM 49-61-00-700-801. FOUND PREVIOUS FLT LEG FAULT 49-31016, OVERTEMP SHUTDOWN. NO CURRENT FAULT LOGGED. PERFORMED APU GROUND VERIFICATION OPS TEST, NORMAL APU STARTING AND SHUTDOWN. NO CURRENT FAULT LOGGED REF AMM 49-11-00-710-801.