As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
EICAS MESSAGE "PTRIM MAIN INOP" DISPLAYED DURING CRUISE. THE CREW FOLLOWED QRH AND DISNEGAGED AUTOPILOT PER THE QRH. AFTER EVALUATING OPERATIONAL REQUIREMENTS, THE OPS AND CREW DECIDED TO DIVERT TO MAINTENANCE BASE AIRPORT. THE AIRCRAFT LANDED SAFELY. MAINTENANCE CONFIRMED THE EICAS MESSAGE AND REPLACED HOTIZONTAL STABILIZER CONTROL UNIT. OPS CHECK GOOD. AIRCRAFT WAS RETURN TO SERVICE.