What was found
WHILE LEVELING OFF AT FL410, THE FLIGHT CREW RECEIVED AN AMBER, CABIN ALTITUDE, CAS MESSAGE. THE CREW DONNED THEIR O2 MASKS AND REQUESTED FL380; AT THIS ALTITUDE IT WAS NOTED THAT THE CABIN PRESSURE WAS NOT STABILIZING, SO AN EMERGENCY DESCENT WAS INITIATED. THE CREW DECLARED AN EMERGENCY AND DIVERTED, WHERE THEY LANDED WITHOUT INCIDENT. MAINTENANCE TECHS REPLACED A FAULTY PRESSURE CONTROLLER, PN 2119862-3 AND ACCOMPLISHED OPS CHECKS, WITH NO DEFECTS NOTED. ACFT WAS RETURNED TO SERVICE.