What was found
ON FINAL APPROACH AT ABOUT 5000 MSL, ALT 29.65, THE OUTFLOW VLV OPENED & CABIN DEPRESSURIZED. NOTE, AT FLT 215 THE STD FOR THE ALTIMETERS STARTED TO FLASH. RESET CPC SYS CB`S, PERFORMED CPC 1 & 2 BITE TEST, CHECKED GOOD. IAW TSM 21-31-00-810-810A LOW DIFFERENTIAL PRESS. NOTE, NO HISTORY IN SCEPTRE PAST 90 DAYS.