As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
IAD - INFLIGHT LGA-DFW. AUXILIARY POWER UNIT LOW OIL PRESSURE LIGHT ILLUMINATED IN FLIGHT APU SHUT DOWN. LEFT ENGINE GENERATOR ON MEL. EMERGENCY DECLARED DIVERTED IAD ON ACCOUNT SINGLE GENERATOR OPERATION. FOUND LOOSE SEAL ON AXILIARY POWER UNIT OIL CAP. REPLACED APU OIL CAP, LEFT CONSTANT SPEED DRIVE AND GENERATOR. SYSTEM GROUND CHECKED NORMAL OPERATION.