Published: Jan 2001
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TECHNOLOGY ADVANCES WITHIN THE PAST 15 YEARS have allowed increasingly sophisticated nonvolatile electronic data storage capabilities on automobiles and trucks. This sophistication has come about because of a combination of governmental regulations requiring more precise control of emissions and safety systems, and the cost benefits and inherent precision available with the use of embedded microcomputer (integrated circuit) feedback systems to control formerly all-mechanical vehicle systems. For four decades before that era, all-mechanical systems were reasonably constant in concept and components. However, electronic feedback systems had the advantage of being self-calibrating and self-aligning over the same period of usage in which purely mechanical systems often wandered far out of acceptable tolerances and needed frequent tune-ups. In this new era, self-calibration was essential because federal emission standards mandated that the emissions portion of vehicle drive trains stay in calibration for 50 000 miles or more, and, if a miscalibration was detected, provide a warning indication (lamp) to the operator. The electronic systems made it easy to do that without frequent tune-ups, as well as having the inherent ability to incorporate programmable warning and alarm limits, depending on vehicle platform and regulation year. Early electronic systems required battery power to save continuing data such as hard and intermittent diagnostic trouble codes (DTCs) and running calibration data. Yet, if battery power was lost, all prior saved DTCs and calibration data were lost. When that happened, any DTCs generated by an intermittent problem would not be detected until the vehicle was again run and the problem reoccurred. Additionally, for every battery power loss, engine systems had to “recalibrate themselves” and radio station settings had to be reprogrammed. Starting in the mid-1980s, a new technology was introduced into vehicle systems, Electrically Erasable Programmable Read Only Memory (EEPROM) (Kendall 1987). EEPROM, developed in the 1970s as an adjunct to microcomputer semiconductor memory development, is nonvolatile, which means that after data are written to it, the data are retained even when its power source is disconnected. This technology avoided engine recalibration cycles and lost radio station settings when a battery was changed. The first on-board automotive applications of EEPROM were in electronic odometers, which saved the vehicle cumulative mileage, even if the battery was disconnected. However, even though the cumulative mileage was saved, it could only be read with battery power applied, since the odometer readout was also electronic. In the 1990s, a product with similar nonvolatile storage characteristics, Flash Memory, was introduced into vehicle systems (Intel 1996; See and Thurlo 1995). Flash memory uses an inherently simpler IC device structure for data storage than EEPROM, but, generally, it is only manipulated in multi-byte block sections, whereas EEPROM can be single-byte or block alterable.