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Thread: OBDII information spec request

  1. #1
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    OBDII information spec request

    Does anyone know where to find OBDII Specifications? I know that you can pay $60 or so to buy them online (mmmph) but does anyone know where I can find full specs?

    I'm trying to figure out all commands that can be issued to the unit, especially MODE 6 and 7 information... I've searched high and low on the internet and haven't found anything.

    Thanks for your help!
    IN DEVELOPMENT -- '96 Mustang, lilliput with PII/450 laptop, custom DC-DC power supply, 60GB; Garmin GPS; 802.11g; compact keyboard, small graphical LCDs, OBDII.

  2. #2
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    Never occured to me why those would be useful. All of the test IDs defined by mode 6 are manufacturer specific. J1979 has a whooping half page devoted to mode 7. It gives the same information as mode 3, but in a continuous stream. I don't think either are worth coding for unless you have some specific info on your vehicle make.
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  3. #3
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    well I'm assuming that the continuous mode tests will give you more information like the fuel pulse width... I know that you can get that info but I don't know where.

    Are you sure that is all that MODE 6 and 7 are?
    IN DEVELOPMENT -- '96 Mustang, lilliput with PII/450 laptop, custom DC-DC power supply, 60GB; Garmin GPS; 802.11g; compact keyboard, small graphical LCDs, OBDII.

  4. #4
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    For mode 7, send 0x07 to request test results and it will respond with 0x47 then 2 byte pairs of codes terminated with a 00 00 code. It states "Test results for these components/systems are reported in the same format as the diagnostic trouble codes in Test Mode $03 -- refer to the functional description for Mode $03" It also says "If the test failed during the driving cycle, the DTC associated with that test will be reported. The test results reported by this mode do not necessarily indicate a faulty component/system." So the exact content of what's reported is really up to the manufacturer as they are free to and likely do extend the code list. But I don't see how you can get variable information through this interface, just stateful.

    Mode 6 is completely up to the manufacturer to define as they are the ones engineering the canned tests. It's a lot more extensive in protocol allowing for passed/failed result and test value minimum and maximum ranges to be passed back to the scan tool. I suppose manufacturers could have adopted a standard convention for test IDs, but its not covered in J1979.
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  5. #5
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    I was looking for some of the same information, but never had much luck. I was interested in building an OBDII interface that was more funtional than the ones for sale. It seems that the cheaper ones are much less functional, and my reason for wanting an interface was all the little features.

    Telek, if you have any luck with your project, let me know. I am novice, but I am willing to learn. I still hope to get an interface for my chrysler, but we will see.
    System in the works:
    Celeron 850 or PIII 933, SB Live! Value into a stock 4 channel amp, ATI vid, 10.4" sharp LCD w/ allen's controller, Elo SW touchscreen overlay and controller, GPS, TV tuner, FW DVD drive, 4 port serial card, and some other stuff....

    Loads of ideas.

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