As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON CLIMBOUT FROM PHL CREW RECEIVED AN ANTI ICE WARNING MESSAGE. AIRCRAFT RETURNED TO PHL, LANDING WITHOUT INCIDENT. MAINTENANCE FOUND SENSING ELEMENT A15WK SHORTED TO GROUND. MAINTENANCE REMOVED AND REPLACED ELEMENT AND NO OTHER DEFECTS NOTED. AIRCRAFT WAS RELEASED FOR SERVICE.