As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER APU START "MAINT" BLUE LIGHT ILLUMINATED. GROUNDED - YES. SHUTDOWN APU. ACCOMPLISHED APU BITE CHECK PER FIM 49-60 TASK 801. FAULT READ LOW OIL QUANTITY. VISUALLY CONFIRMED AT APU OIL SIGHT GAUGE THAT OIL LEVEL IS FULL. PERFORMED APU BITE CHECK AGAIN - OIL QTY FULL, BLUE MAINT LIGHT EXTINGUISHED. RAN APU - BLUE MAINT LIGHT REMAINED OUT.