As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON DEPARTURE FROM MKE CREW NOTED CABIN WAS EXCESSIVELY WARM AND HAZY. ALSO NOTED A LOUD IN RUSHING AIR NOISE. CREW RETURNED TO MKE. MAINTENANCE DETERMINED THE ENVIRONMENTAL CONTROL SYSTEM CONTROLLER WAS CAUSING THE EMERGENCY PRESSURIZATION VALVE TO OPEN UNCOMMANDED. THE ECS WAS REPLACED WITH AN OVERHAULED UNIT. OPERATIONS CHECKED GOOD.