Since the 1988 model year, California has required manufacturers to monitor the emissions-control components on vehicles sold in the state.
The first monitoring systems, known as OBD-I, were limited in scope. They gave way to today's more sophisticated OBD-II technology.
Under the Clean Air Act Amendments of 1990, the EPA began mandating OBD-II systems nationwide.
SAE developed the standard 16-pin OBD connector and the standard diagnostic trouble codes.
That opened the door for the development of hand-held scanning tools for extracting diagnostic codes and the development of other data loggers and dongles, all with easy access to the OBD port and the valuable data that it leads to.
Sriram Venkatraman, industry principal for automotive IT and transportation at research firm Frost & Sullivan, says insurance companies and fleet managers looking into vehicle behavior were among the first outside companies to tap into onboard diagnostics.
The downside: OBD-II ports are notoriously easy entry points for hackers. Dongles used to plug into OBD-II ports to pull data for insurance purposes, for example, have been a particularly fertile target.
"My recommendation is never connect anything there," says Dan Sahar, vice president of product at Upstream, an Israeli automotive cyber-security firm.
"There's a falsehood being circulated around that OBD ports are 'read only'. Unfortunately, the OBD protocol is 'read-write.' Your app might be read-only, but the underlying infrastructure is read-write.
"All you have to do as a hacker is replace software that only reads with a version that can also write. The protocol allows that, so 'read only' doesn't ensure security. I would definitely not plug anything into the OBD port."
OBD technology has a fairly long history.
According to some published reports, Volkswagen was likely the first automaker to equip a car with a scannable OBD port. It was VW's 1968 Type 3, which boasted an electronically controlled gasoline injection system pioneered by Bosch.