As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FWD EQUIPMENT VALVE EICAS MSG. A/C RELEASED ON MEL 21-58-01-01, MDDR 134712, CAT 'C'.< : MIX MANIFOLD VALVE PREVIOUSLY CHANGED. PERFORMED OPS CHECK IAW AMM 21-58-00. NO FAULTS NOTED. PERFORMED ENGINE RUN OF BOTH ENGINES IAW AMM 71-00-00 AND CONFIRMED VALVE WAS IN COMMAND POSITION PER MEL 21-58-00.