What was found
AIRCRAFT WAS NOT GROUNDED. AIR INTERRUPT, EMERGENCY DECLARED, LANDING UNEVENTFUL. AIRCRAFT OVERWEIGHT. DURING CLIMB THROUGH APPROXIMATELY 22,000 FT RECEIVED AN OUTFLOW VALVE AFT MESSAGE. MAINTENANCE ACCOMPLISHED CABIN PRESSURE CONTROL SYSTEM TEST IAW DMC 787-A-21-31-00-03A-320A-A AND MANUAL MODE CONTROL TEST IAW DMC 787-A-21-31-00-02B-320A-A WITH NO FAULTS FOUND. SYSTEM CHECKS NORMAL.