As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING AFTER START CHECK, BLUE APU MAINTENANCE LIGHT ILLUMINATED. APU OPERATION WAS NORMAL. ACFT GROUNDED. WHEN ENTERING FLIGHT DECK FOUND MAINTENANCE LIGHT OFF AND APU OFF. ACCOMPLISHED BITE CHECK WITH NO FAULTS. APU OIL LEVEL IS FULL. PERFORMED APU START WITH ALL PARAMETERS NORMAL.