In 1970, the U.S. congress passed the Clean Air Act to reduce air pollution. Auto manufactures began to adopt electronic devices into their newer vehicles to meet criteria. Surprisingly early types of diagnostic link connectors (DLC) were already introduced at that time. And also catalytic converter, electronically controlled fuel injection and ignition system were introduced in the 70′.

In 1980, General Motors introduced ALDL, Assembly Line Diagnostic Link. The only function is to blink check engine light. With ignition key on and engine off, connecting pin A and B, check engine light blinks. You need to count time of blinks and duration and then look up in diagnostics chart to know what problem a vehicle have.

In 1986, the foundation of California Air Resources Board (CARB) start strictening regulation. All cars sold in the state required OBD system to detect emission failures, first in California and then the other states. Later on, this system would be called OBD1. OBD1 couldn’t detect failures of catalytic converter and evaporative emission system. Besides, because of lacking of standardarization, shapes of data link connector (DLC) varied from manufacture to manufacture, even between models of the same manufacture.

In 1988, the Society of Automotive engineers (SAE) suggested to use the same shape of connector as well as pins functioning the same manner.

In 1996, the OBD2 became mandatory for all passenger cars and light trucks sold in the U.S..

In 2001, the European Union made EOBD (european on-board diagnostic) mandatory for all gasoline cars sold in the European Union. Three years later, 2004 for all diesel cars.


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