As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE IN CRUISE AT FLIGHT LEVEL 40000 THE ICAS CABIN PRESSURIZATION FAULT DISPLAYED. WENT TO MANUAL AS PER THE CHECK LIST AND THE CABIN ALTITUDE WAS UNCONTROLLABLE.///SIGN-OFF///REMOVED AND REPLACED RIGHT ENGINE AND AIRFRAME I/O UNIT (GEA7100 #3) IAW CE680A AMM 31-30-00, 31-40-15 AND 42-10-01. OPS CHECK GOOD.