In 1975, the Datsun 280Z had an on-board computer that helped make fuel injection adjustments. By 1980, GM had a built-in Engine Control Module on California cars, although the device was only for pre-delivery testing.

In 1988, the Society of Automotive Engineers outlined a 16-prong connector and standard diagnostic test signal protocols required on all vehicles sold in the United States.

On-board car computer systems are now a fact of life. The complications begin when each of the car