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 A CIDS PANEL CAUTION LIGHT FOR THE AFT CARGO DRAIN MAST HEATER FAIL. THE AIRCRAFT LANDED SAFELY AT DFW AND TAXIED TO THE GATE UNDR ITS OWN POWER. MAINTENANCE REPLACED THE AFT CARGO DRAIN MAST AND ACCOMPLISHED A SATISFACTORY OPERATIONAL CHECK PER AMM 30-71-51.