As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: AN EMERGENCY WAS DECLARED AND THE AIRCRAFT RETURNED TO DFW DUE TO THE FLIGHT CREW REPORTING WITH ENGINE 1 IDG INOPERATIVE AND ON MEL THE APU AUTO SHUTDOWN WHILE PASSING FL 290 - THE AIRCRAFFT LANDED SAFELY AT DFW WITHOUT FURTHER INCIDENT - MAINTENANCE FOUND AN APU OIL PRESSURE SWITCH FAULT MESSAGE ON THE MCDU AND REPLACED THE PRESSURE SWITCH PER AMM 49-94-14