As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CSS REQUEST ON DISPATCH RELEASE. FIRST START AT 36000 FT APU FAULT LIGHT ILLUMINATED. FAULT LIGHT EXTINGUISHED IMMEDIATELY AFTER SWITCH POSITION TO OFF. SECOND START 3 MINUTES LATER SUCCESSFUL. ACFT GROUNDED. APU INOPERATIVE CDU FAULT CODE 49-31175 - FAULT LIGHT FCU RESOLVER CIRCUIT SHOWS BAD. NO OBVIOUS DAMAGE TAIL AREA. REPLACED APU FCU IAW AMM 49-31-11. LEAK AND OPS CK GOOD.