As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE SERVICING APU, FOUND OIL FLITER INDICATOR DELTA-P INDICATOR TRIPPED. ACFT GROUNDED. R & R OIL FILTER, RESET DELTA-P INDICATOR. INSPECTED MAG DRAIN PLUG, NO CONTAMINATION NOTED. RAN APU NO LEAKS NOTED. REF AMM 49-91-81-200-801, AND 49-91-12-400-802.