As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DFW INFLIGHT T1310/19 APPROACHING 14,000 FEET AFT CARGO FIRE INDICATION AND MASTER WARNING LIGHTS CAME ON. DISCHARGED NR 1 FIRE BOTTLE. NO INDICATION OF DISCHARGE. FOLLOWED QRH AND RETURNED TO DFW. LANDED WITHOUT INCIDENT. FOUND ON R2-5 RELAY A GROUND CONTROL WIRE MIS-WIRED FROM CARGO SMOKE CONTROL PANEL. REPLACED R2-5 GROUND CONTROL RELAY. SYSTEM GROUND CHECKED NORMAL OPERATION.