What was found
FLT 2002, JFK-BUF. DURING CLIMB AUTOPILOT OFF, PITCH TRIM ACTIVATED ON ITS OWN. PITCH TRIM FAIL, AUTOPILOT FAIL CAUTION EICAS ALONG WITH MACH TRIM FAIL, AUTOPILOT/TRIM DISCONNECT HELD DOWN. COMPLIED WITH QRH. SYSTEM RESET AFTER QRH PROCEDURE. ON FINAL APPROACH AUTO PILOT OFF, PITCH TRIM ACTIVATED ON ITS OWN, AP/TRIM DISCONNECT HELD DOWN UNTIL TOUCHDOWN,SYS 1 SYS 2 CUTOUT SWITCHES TO OFF. ACTIVE MESSAGES AP FAIL PITCH TRIM FAIL STALL PROTECT FAULT MACH TRIM FAULT; REMOVED AND REPLACED HSACE IAW AMM 27-43-01 PERFORMED OPS CHECK PER 27-40-00. OPS CHECK GOOD NO FAULTS NOTED. PERFORMED RTS PER AMM 27-00-00-070-801. NO FAULTS NOTED. A/C OK TO CONTINUE.