As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CLIMB OUT FROM MSP APU LOW OIL PRESSURE LIGHT ILLUMINATED FOLLOWED BY #2 SOURCE OFF LIGHT ILLUMINATING. DECLARED AN EMERGENCY- AIR RETURN. REMOVED AND REPLACED APU LOW OIL PRESSURE SWITCH IAW AMM 49-94-22. DPI INDICATOR INSPECTED, OIL LEVEL FULL. OK FOR SERVICE.