As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CABIN DIFF DURING FLIGHT INDICATED 0. CABIN ALT REMAINED AT = 3000' DURING FLIGHT A DESCENT. CABIN RATE OF CLIMB INDICATED 0 DURING FLIGHT. NO FAULT ON CPC. AIRCRAFT WAS PRESSURIZED. (CABIN DIFF PRESSURE INDICATOR - UNPRESSURIZED). REMOVED FROM SERVICE. FOR R&R OF CABIN INDICATION MODULE. PERFORMED FUNCTIONAL TEST OF THE PRESSURIZATION CONTROL IAW AMM 21-31-00-720-801. CABIN DIFF PRESSURE INDICATES NORMALLY. PLACARDS REMOVED, CLEARS MEL. AIRCRAFT RETURNED TO SERVICE.