As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING TROUBLESHOOTING FOR INOPERATIVE AUTOPILOT PITCH TRIM, RECEIVED A RUDDER SERVO FAULT INDICATION ON ACFT MX DIAGNOSTIC COMPUTER. REPLACED THE RUDDER SERVO WITH AN O/H SERVO. NO FAULT INDICATIONS NOTED, OPS NORMAL. RECOMMEND SERVO MFR INVESTIGATE FAIL INDICATION AT INCOMING INSP.