What was found
AT ALTITUDE CABIN PRESSURE INDICATED 20460 AND COMMANDED DESCENT. DONED MASKS AND DESCENDED TO 10K, DIVERTED. CABIN PRESS INDICATIONS DELTA P XX (ORANGE) V/S= 2950 (ORANGE) CABIN ALTITUDE 20460 (RED) WHEN EVENT OCCURRED BOTH CREW HAD EARS POP. BELL SOUNDED REMINDER OF FLIGHT. AT SHUTDOWN, CABIN FILLED WITH DENSE CONDENSATION. VISIBILITY ZERO FOR SEVERAL SECONDS. (SAFETY VALVE OPENED). CHECKED CPC CABIN PRESSURE CONTROLLER. CABIN ALT INDICATED AT 80 FT AT ALL TIME. R & R NR 2 CPC IAW MM 21-31-11-04 AND BITE TEST OK. PERFROMED CABIN PRESSURE CHECK WITH APU AIR TO 8.3 PSI. SAFETY VALVE CRACK OPEN AND CLOSE AS THE PRESSURE INCREASED AND DECREASED AROUND 8.3 PSI. SAFETY VALVE FUNCTION CHECK NORMAL. ACFT RELEASED FOR SERVICE.