As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FAULT LIGHT ILLUMINATED WHEN STARTING APU, AUTOMATICALLY SHUT DOWN. RESTART ATTEMPTED AFTER 5 MINUTES, FAULT LIGHT RETURNED. ACFT GROUNDED. FOUND APU OIL FILTER DPI TRIPPED. COMPLIED WITH AMM 49-91-13-600-801 INSPECTED MAGNETIC DRAIN PLUG, NO DEFECTS NOTED. REPLACED LUBE FILTER ELEMENT AND RESET DPI INDICATOR REPLACED STARTER GEN ASSY IAW AMM 49-41-21-400-801. PERFORMED GROUND VERIFICATION WITH NO DEFECTS NOTED AND DPI REMAINED SET.