As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE FLIGHT CREW REPORTED A STABILIZER MAIN PITCH TRIM RUNAWAY. THE AIRCRAFT DIVERTED SAFELY TO PSM. THE PITCH TRIM RELAYS K021 AND K022 P/N 974.20.01.212 WERE REMOVED AND REPLACED, AND THE STABILIZER TRIM SYSTEM TESTED GOOD IAW THE PILATUS AMM 12-A-27-40-00-00A-903A-A. MX OBSERVED THE "AURAL WARNING TONE" OF A STAB TRIM RUNAWAY WAS REPRODUCEABLE ON THE GROUND AFTER ARRIVAL. HOWEVER THE STAB TRIM ACTUATOR DID NOT MOVE DURING THIS TROUBLESHOOTING WHILE THE "WARNING TONE" WAS ACTIVATED.