As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CASS MESSAGE "YD FAIL UPPER A" AFTER TAKOFF. AFTER TAKING OFF FROM KMDW WITH THE CASS MESSAGE THE PILOTS RETURNED TO KMDW. ONCE THE PILOTS WERE ON THE GROUND THEY PERFORMED A REBOOT OF THE ELECTRICAL SYSTEM AND THE FAULT DID NOT RETURN.