As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON GROUND TRIED TO START APU, WOULD NOT START W/ FAULT LIGHT ILLUMINATED. AFTER 5 MINUTES FAULT LIGHT EXTINGUISHED. ACFT GROUNDED. R & R APU IGNITION UNIT REF AMM 49-41-31, R & R APU IGNITION LEAD REF AMM 49-41-52. OPS CHECK NORMAL, APU STARTS NO CURRENT FAULTS LOGGED.