As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CREW REPORTED LT DUCT OVERHEAT RED WARNING MESSAGE. AIRCRAFT RETURNED TO MKE LANDING WITHOUT INCIDENT. MAINTENANCE REMOVED AND REPLACED THE CONTROL BLEED AIR UNIT PER THE AIRCRAFT MAINTENANCE MANUAL. OPERATIONAL CHECKS WERE PERFORMED PER THE AIRCRAFT MAINTENANCE MANUAL. AIRCRAFT WAS RELEASED FOR SERVICE.