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OBD-II Standards Information Page

    When we started the OBD-II Diagnostic Scanner product development, finding information about OBD-II was difficult at best.  Most web sites had a little vague information and when we finally found the specs, the titles were often mis-leading as to the content.  All of the information although public is copyrighted and you can't just put copyrighted documents out for general download.  We sure burned through a lot of time and money buying and reading specs we didn't really need.  Here, we will tell you what the spec numbers are, where to get them and a general overview of their usefulness.  If you have a specific question, drop us an e-mail, and we'll try to help you out.  We won't send copies of documents, so don't ask.

    The specs generally fall into three categories. 

    All of those come from two sources

    If the spec isn't listed below, we didn't find it useful enough to list but we did list some to avoid even though the title is enticing.  Be careful, a lot of publications have titles made to make you buy but often have little substance. 

A book is available from SAE called 'HS-3000 On-Board Diagnostics for Light and Medium Duty Vehicles' and all of the 'J' specs referenced below are in it and then some.  Make sure you get the 2003 version.  Well worth the $140.

   

    End User Tool Spec

 J1978 - Describes what the user interface should look like and a minimum set of functionality.  It provides no information about data requests

    Bit Level Specs

J1850 - Describes in detail voltage levels, bit timing, and message packaging for PWM and VPW

J1962 - Describes the OBD-II connector and pin-out.  This info can also be found on this site in the Cables section.

ISO-9141-2 - Describes in detail, voltage levels, bit timing and message packaging for ISO-9141 and ISO-14230.  Also describes how to initialize the ISO-9141 bus for communication.

ISO-14230-2 - Describes how to initialize the ISO-14230 bus for communication.  The actual communication is defined in ISO-9141-2

    Message Level Specs

J1979 / ISO-15031-5  - Describes in detail the mandated emission related communications.  (A must have)

J2012 - Diagnostic Trouble Code Definitions.  This only has the generic codes and you can find them on-line easy enough.

J2190 - Enhanced Diagnostic Test Modes.  This was a real let down.  To summarize, you must use physical addressing, mode $22 is for 2 digit enhanced PID's, mode $13 is for all DTC's ;and mode $14 Clears DTC's.  If you don't have a blueprint of the manufacturer specific information, it just isn't worth the money.

J2178 parts 1 thru 4 - Part 1 defines how the 3 byte header is made up and gives a table of physical device addresses.  Part 4 defines the list of functional addresses.  Really not needed unless you're looking into J2190.  If you are looking for info to implement J1979, it's in J1979, you won't get anything out of this.

 

 

Copyright © 2004 [Bowser Electronics]. All rights reserved.
Revised: 10/22/09