Tom Boynton
CET 249
December 2006
General Motors Computerized Vehicle Control Systems: A Short History
The modern automobile has progressed greatly in the last 100 years. Just as our everyday
consumer life has become sophisticated, our transportation has followed suit. Just how
complex the modern automobile has become, though, is most likely not known by the
average person. We see all the high tech gadgets nowadays, high speed internet, high
speed computers and fancy entertainment systems, these concepts are all in the modern
car. This paper will explain a few details of our modern automotive computer systems.
To understand the need for automotive networks, a short explanation of a cars
electrical system is necessary. The earliest vehicles started out with some primitive
control systems. The ignition coil for firing the fuel charge in the internal combustion
engine was ìclockedî by the ignition points and timed to the engines firing order. It was
a basic mechanical system and was not always the most efficient as it relied on a
mechanical devices to provide timing which followed a set curve and had moving parts to
wear out. Numerous moving contact type controls for different parts of vehicles tended
to fail or wear out quickly due to the harsh conditions present in cars such as heat, cold
and continuous vibrations. Modern solid state control systems started to appear in the
early seventies as transistor technology and cheaper solid state products entered the
market. The transistor provided an excellent way to incorporate things such as the
ignitionís mechanical points into electronic ignition modules which didnít require
maintenance, were much more reliable and could be produced cheaply. Other things that
helped bring about a change in automobile management systems was the need to more
precisely control a vehicleís engine systems so as to keep up with increasing emissions
and fuel economy standards.
In the early sixties, with automobile production soaring and Eisenhowerís new
federal highway system making automobile travel much easier, people started to realize
that the Earthís atmosphere was getting increasingly polluted from the noxious fumes that
were belching out of the automotive jungle. Large cities such as Los Angeles and New
York City were developing large smog problems and there was some need to improve the
amount of pollution entering our atmosphere. The Clean Air Act in 1967 started a trend
in controlling our vehicles very precisely to clean up our urban areas.
The first Clean Air Act only did very minimal things such as requiring the
crankcase gases to be a closed system and nitrous oxides emissions to be reduced with an
2
EGR system. The really big change came in 1980 with the initiation of the revised 1977
version of the Clean Air Act which set some higher emissions standards, outlawed leaded
gasoline, introduced the catalytic converters as mandatory equipment and required
vehicles to monitor their emissions controls with a light on the dashboard called the
ìcheck engine lightî.
← This is a modern computer case. You
can see the case is much thicker than the old
case below it. The small access cover on the
top is for the electronic spark control (knock
sensor) module which is removable. The
removable PROM is now an EEPROM and is
hard soldered to the circuit board.
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