Serial Data Communication ProtocolsWhen multiple on-board computers need to communicate with each other, they must speak the samelanguage (protocol) at the same speed (baud rate). Starting in 1996, U.S. EPA regulations require that all automobile manufacturers establish a commoncommunications system for emissions related controllers. As it turned out, there were four differentprotocols used with a common data link connector (DLC). This section describes the four differentcommunication protocols used by most automobile manufacturers since 1996. Starting in 2008, U.S. EPA regulations require that all automobile manufacturers use a single commoncommunications protocol for emissions related controllers. This section describes the new standardizedcommunication protocol; Controller Area Network (CAN).The most significant result of these regulations is that the regulation provides the scan tool manufacturers
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