The OEM databus in cars got its start in the mid-1980s when automakers used the term “multiplexing” to describe how they would send control signals, radios, power door locks and windows, taillights, and other “loads” over a single wire connecting all devices in series. Eventually OEM security systems and outboard OEM amplifiers would be tied into multiplexed systems.
The technology confounded the aftermarket for a time, but the aftermarket has begun to cope with aftermarket security systems and head units that integrate with the factory databus to maintain other OEM-system functions.
The first prototype databus systems were not so elegant, as I was reminded when I plucked this picture from the TWICE archives. It pictures a 1980s prototype of steering wheel-mounted controls built on a databus system. I think it was from Chrysler.
The steering wheel hub contains controls for the radio, lights, wipers and cruise control system, and as the picture shows, it’s “computer-equipped.” It’s not so elegant-looking, but it pointed the way to the future of automotive electronics systems and the aftermarket.