As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
BWI - FL 26, AFTER TAKEOFF, CREW REPORTED LOSING MANUAL TRIM. AUTOPILOT WAS SELECTED TO DETERMINE ITS CONTROL CAPABILITY. AUTOPILOT COULD NOT TRIM UP OR DOWN. EICAS MESSAGE 'AUTOPILOT' ILLUMINATED. FLIGHT RETURNED TO BWI AND LANDED WITH NO FURTHER INCIDENT. MAINTENANCE REPLACED THE LEFT POSITION TRANSMITTER. (M)