As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE FLIGHT CREW REPORTED RECEIVING AN AUTO-PILOT AND YAW DAMPENER FAIL MESSAGE; NEITHER WOULD ENGAGE. THE MAINTENANCE VENDOR TROUBLESHOT DETERMINED THE ELEVATOR ACTUATOR SERVO WAS DEFECTIVE. THE DEFECTIVE SERVO ACTUATOR AND INSTALLED AN OVERHAULED UNIT. FUNCTIONAL CHECKS WERE SATISFACTORY AND THE AIRCRAFT WAS RETURNED TO SERVICE.