As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
MI 0330Z FL 350 DIVERT TO KIN FOR CABIN ALTITUDE LIGHT ON EICAS. CABIN ALTITUDE/OUTFLOW VALVE UNCONTROLLABLE. CABIN ALTITUDE REACHED 14000 FEET. BELOW 18000 FEET AUTOMATIC CONTROLLER APPEARED TO WORK NORMALLY. OUTFLOW VALVE TESTED ON THE GROUND IN MANUAL, WORKS NORMALLY. DEFERRED PER MEL 21-31-1A CAT C. PEFORMED FIM 21-31 FAULT TREE 803, FOUND 1&2 AC MOTOR FAULTY. REMOVED AND REPLACED OUTFLOW VALVE PER AMM 21-31-03 POST INST TEST OK.