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 ON TAKEOFF WITH LEFT GENERATOR ON PLACARD. EMERGENCY DECLARED FLIGHT RETURNED DFW LANDED WITHOUT INCIDENT. AIRCRAFT REMOVED FROM SERVICE. SHUTDOWN AND RESTARTED APU, RAN APU FOR 20 MINUTES NO FAULTS NOTED. REPLACED LEFT GENERATOR. SYSTEM GROUND CHECK NORMAL OPERATION.