As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CREW REPORTED AN APU OIL PRESSURE CAS LIGHT ON AT CRUISE AFTER TAKEOFF FROM TYS. THE AIRCRAFT RETURNED TO TYS AND LANDED WITHOUT INCIDENT. MAINTENANCE INSPECTED THE APU ELECTRONIC CONTROL UNIT (ECU) PER THE AIRCRAFT FAULT ISOLATION MANUAL. NO FAULTS WERE FOUND. MAINTENANCE INSPECTED ALL CONNECTORS. NO DEFECTS WERE NOTED. MAINTENANCE PERFORMED OPERATIONAL CHECKS PER THE AIRCRAFT MAINTENANCE MANUAL. AIRCRAFT WAS RELEASED FOR SERVICE.