As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ATBH: APU FAILED TO START, FAULT LGT ILLUM. AND EICAS MSG APU FAULT DISPLAYED 4904554 012353 000819 001 02. DID BITE OF ECU PER FIM 49-11-00 SHOWS NO LIGHT. REPLACED IGNITER PLUG AND LEAD NO HELP. REPLACED EXCITER BOX WITH LOANER BOX FROM UAL. APU STARTS NORMALLY APU OPERATION NORMAL.