As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON FLIGHT 3967 AFTER TAKEOFF AT APPROXIMATELY 500 FEET THE CREW RECEIVED A " MAIN PTRIM INOP " EICAS MESSAGE. THE CAPTAIN’S AND THE FIRST OFFICER’S PITCH TRIM SWITCHES DID NOT OPERATE. THE CREW RETURNED AND THE AIRCRAFT WAS REMOVED FROM SERVICE. REMOVED AND REPLACED THE HORIZONTAL STAB CONTROL UNIT IAW EMB-145 AMM 27-40-01. THE OPERATIONAL CHECK WAS GOOD. THE AIRCRAFT WAS RETURNED TO SERVICE.