As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APU FAILED TO START ON THREE ATTEMPTS. FAULT LIGHT ILLUMINATED WITH MAINT MESSAGE 49-41181, IGNITION UNIT CIRCUIT SHOWS OPEN. CYCLED AUX PWR UNIT CIRCUIT BREAKER. NO HELP. ACFT GROUNDED. REPLACED APU IGNITER PLUG, LEAD, AND APU IGNITION UNIT IAW MM 49-41-51-400-801 AND 49-41-52-400-801 AND 49-41-31-400-801. OPS CHECK NORMAL.