EPROMs & EEPROMs: Introduction
WARNING: This page does not describe the selected car, but rather 333 other vehicles, including the 2007 BMW Z4, 2007 BMW X5, 2007 BMW X3, 2007 BMW M6, and 2007 BMW M5. However, it is still accessible from the selected car via links, so may be relevant.
Early Engine and Transmission Control Modules used EPROMs (Electrically Programmable Read Only Memory device) to store operational programs and operating data specific for the application that they were used for. Since the operating program and associated data is installed at the factory during the vehicle assembly process updates could not be provided for vehicles once they were programmed and left the factory floor. In order to install a new or updated program (DME or TCM) the module needed to be replaced. Eventually it became possible to replace EPROMs and/or update them which dramatically reduced the cost of updating a module and a vehicle.