As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED. FLIGHT CREW REPORTED A FLIGHT CONTROL SYSTEM 1 FAULT INDICATION. AN EMERGENCY WAS DECLARED AND THE AIRCRAFT RETURNED TO DFW WHERE IT LANDED SAFELY WITHOUT FURTHER INCIDENT. REPLACED SLAT POWER CONTROL UNIT BLOCK VALVE AND ACCOMPLISHED A SATISFACTORY OPERATIONAL CHECK PER AMM 27-84-53.