As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APU FAILED TO START. RECEIVED A FAULT LIGHT AND MAINT MESSAGE 49-41180. ACFT GROUNDED. STARTED APU NUMEROUS TIMES SUCCESSFULLY. FAULT CODE DOES NOT REAPPEAR. OPS CHECKED GOOD IAW FIM 49-40, TASK 804. REMOVED AND REPLACED APU IGNITION EXCITER OPS CHECKED GOOD. REF. AMM 49-41-31.