As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AT 800 FT AFTER TAKEOFF, BOTH STAB TRIM CHANELS DISENGAGED (AND MACH TRIM), FOLLOWED QRH PROCEDURE, COULD NOT CLEAR MSGS. RETURNED TO DFW. PERFORM SYSTEM CHECK ON HSTCU. SYSTEM CHECK OF HSTCU, PERFORMED NORMALLY. OPERATED STAB TRIM & MACH TRIM. BOTH SYSTEMS CHECK GOOD IAW CL 600 MM 27-40-00. COULD NOT DUPLICATE SQUAWK.