What was found
AT FL 360, PRESSURIZATION SPIKED TO MAX PSI, NO HELP IN ALTERNATE & NO ANNUNCIATORS ILLUMINATED. FLIGHT DIVERTED USING MANUAL MODE, AN EMER WAS DECLARED & THE FLIGHT LANDED WITHOUT FURTHER INCIDENT. ACFT WAS REMOVED FROM SERVICE, APPLIED MEL. R & R AFT OUTFLOW VLV ASSEMBLY IAW AMM 21-31-03. OPERATIONALLY CHECKED GOOD AT THIS TIME, CLEARED FROM MIC SHEET & REMOVED PLACARD.