As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLIGHT 4985 - RECEIVED ANTI-ICE DUCT WARNING CAUTION MESSAGE. RETURNED TO PHL, LANDED WITHOUT INCIDENT. PERFORMED TESTS OF ANTI-ICE AND LEAK DETECTION CONTROLLER, AND THE WING ANTI-ICE CONTROL INDICATION SYSTEM. NO DEFECTS NOTED. AIRCRAFT RETURNED TO SERVICE.