As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING FLIGHT, AIRCRAFT HAD ABRUPT PITCH DOWN AND TRIM RAN AWAY CAUSING RAPID DESCENT. PILOT DISENGAGED AUTOPILOT AND AIRCRAFT HAD ABRUPT PITCH CHANGE. TROUBLESHOOTING REVEALED BAD PITCH SERVO COMMANDING TRIM TO RUN. AIRCRAFT PASSED GROUND SELF-TEST, YET UPON ENGAGEMENT, TRIM RUNS AWAY. REPLACED PITCH SERVO AND FUNCTIONAL TESTED GOOD.