As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APU FAILED TO START WITH ACCOMPANYING FAULT LIGHT. GROUNDED - YES. APU BITE SHOWS IGN UNIT HIGH CURRENT (MAINT MSG 49-41180) NO FLAME SHUTDOWN. TAIL INSP NORMAL. PERFORMED B737-800 FIM 49-40 TASK 804. INITIAL EVALUATION. IT WAS INTERMITTENT FAULT. OPS CHECK APU MULTIPLE TMES, OPS CHECKED GOOD. CANNOT DUPLICATE FAULT.