As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
IN CRUISE FLIGHT MAIN PITCH TRIM WAS ENGAGING BY ITSELF CREW DROP OFF AUTO PILOT AND IT WAS STILL DOING IT. CALLED MOC AND HAD THE CREW PULL THE NO 1 TRIM C/B STILL DID NOT HELP. CREW ELECTED TO DIVERT TO GET THE AIRCRAFT ON THE GROUND AS SOON AS POSSIBLE. C/A: MAINTENANCE REMOVED AND REPLACED THE HSCU IAW MM. OPERATIONAL CHECK WAS GOOD AND AIRCRAFT WAS RETURNED TO SERVICE.