As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CREW REPORTED THAT ON CLIMB-OUT FROM MKE, RECEIVED A RUDDER SYS 1-2 INOP MESSAGE ALONG WITH A YAW DAMP FAIL MESSAGE ON EICAS. THE QRH WAS FOLLOWED AND THE MESSAGE CLEARED, BUT RETURNED AFTER ABOUT 5 MINUTES. THE QRH WAS FOLLOWED AGAIN AND THE MESSAGE CLEARED, AND IT WAS DECIDED TO RETURN TO MKE WHERE THE AIRCRAFT LANDED WITHOUT INCIDENT. MAINTENANCE REPLACED THE NR 2 RUDDER PRESSURE SWITCH AND THE RUDDER SYSTEM OPERATED NORMALLY. THE FAULT RETURNED ON THE NEXT FLIGHT TO SDF AND THE NR 2 PRESSURE SWITCH WAS FOUND TO BE BAD FROM STOCK. THE NR 2 PRESSURE SWITCH WAS REPLACED AGAIN WITH NO FURTHER DIFFICULTIES.