As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) AFTER TAKEOFF, EICAS MESSAGE "CABIN ALT AUTO 1 APPEARED. AIRCRAFT DIVERTED TO LONDON (HEATHROW) LHR FOR FIX. OUTFLOW VALVE AND ACTUATOR REPLACED AS PER AMM 21-31-02. SYSTEM CHECKED SERVICEABLE.OUTFLOW VALVE -606832-21 ACTUATOR -2022480-6