quick answer would be ecm but since i have no idea what you drive and not sure the size from the pic its quite possibly a control module for a specific system... its has oem looks to it but i see a white card, does it have any kind of product info or installation instructions?
you seem very mediocre with car knowledge i think you need to learn more before delving right into electrical systems especially this important component of whichever system it controls. its possible to be a rechipped ecm, is it even an eprom, eeprom, cant tell. its possible the one in the car has something physically wrong with it and hasnt failed yet