The SAE J1939 series of recommended practices are intended for light- and heavy-duty vehicle uses on- or off-road as well as appropriate stationary applications which use vehicle-derived components (e.g. generator sets). Vehicles of interest include, but are not limited to: on- and off-highway trucks and their trailers, construction equipment, and agriculture equipment and implements.
The purpose of these documents is to provide an open interconnect system for on-board electronic systems. It is the intention of these documents to allow electronic devices to communicate with each other by providing a standard architecture.
J1939-73 identifies the diagnostic connector to be used for the vehicle service tool interface and defines messages to accomplish diagnostic services. California-regulated OBD II requirements are satisfied with a subset of the specified connector and the defined messages. Diagnostic messages (DMs) provide the utility needed when the vehicle is being repaired. Diagnostic messages are also used during vehicle operation by the networked electronic control modules to allow them to report diagnostic information and self-compensate as appropriate, based on information received. Diagnostic messages include services such as periodically broadcasting active diagnostic trouble codes, identifying operator diagnostic lamp status, reading or clearing diagnostic trouble codes, reading or writing control module memory, providing a security function, stopping/starting message broadcasts, reporting diagnostic readiness, monitoring engine parametric data, etc.
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Changes in the January 2010 Version include: Figure H1, far right box should have DM12 not DM11. New appendix added to fully describe lamp status and lamp flash. Text added to clarify format of messages with DTCs. Appendix A was updated to provide more specific guidance on the FMIs to use when declaring OBD DTCs. Corrected DM19 figures to refer to the correct Acknowledgement PGN. More DM19 changes to clarify byte order for Cal ID transmission. Also identified DM19 response while CVN is first being computed with recommended retry time. A DM7 and DM30 convention was established to report test results for all tests of one SPN (i.e. a system or component is identified with a specific SPN). Added appendix J to clarify OBD readiness bit construction. The title to section 18.104.22.168 is corrected to EI AECD. Added clarifications to OBD readiness information for the Exhaust Gas Sensors.