As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON FLIGHT 3483 DURING CRUISE THE CREW REPORTED THAT THE PRESSURIZATION WAS UNCONTROLLABLE IN AUTO AND MANUAL MODE. THE CREW ELECTED TO DIVERT TO ATL AND LANDED WITHOUT INCIDENT. THE AIRCRAFT WAS REMOVED FROM SERVICE. REMOVED AND REPLACED THE VACUUM PUMP IAW AMM 21-31-06. THE PRESSURIZATION CHECKS WERE GOOD. THE AIRCRAFT WAS RETURNED TO SERVICE.