As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DFW - EN ROUTE DFW-PHL SMOKE IN CABIN. RETURNED DFW AND LANDED WITHOUT INCIDENT. FOUND LOOSE HYDRAULIC LIGHT TEE FITTING ABOVE LEFT HAND THRUST REVERSER CONTROL VALVE. TIGHTENED HYDRAULIC LIGHT TEE FITTING ABOVE LEFT HAND THRUST REVERSER CONTROL VALVE. ACCOMPLISHED PACK BURNOUT PER CARD 21 92 12. SYSTEM GROUND CHECKED NORMAL OPERATION.