As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DFW CREW REPORTED AUXILIARY POWER UNIT FAILED WITH AC CROSS TIE ON PLACARD. EMERGENCY DECLARED FLIGHT RETURNED DFW LANDED WITHOUT INCIDENT. AIRCRAFT REMOVED FROM SERVICE. REPLACED AUXILIARY POWER UNIT. SYSTEM GROUND CHECKED NORMAL OPERATION CLOSED