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How to send commands to ELM327 OBD interface

Discussion in 'Electronic Design' started by powerampfreak, Nov 24, 2012.

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  1. Hello!
    I'm looking for information how to send commands to the popular ELM327 OBD interface. I want to design a stand alone device that check long term fuel trim values along with some other parameters.
    Is there a good guide somewhere how those commands are set up?
    Thanks in advance
  2. miso

    miso Guest

    It looks like the device you buy is just a packaged version of the chip
    and a bit of glue electronics. Is the actual datasheet useful?
  3. Great guys!
    ELM327 is a pre-programmed PIC processor. It communicates by RS-232, so probably I can set up another PIC through the USART and communicate with the ELM.
    And possibly use a 2x16 char LCD display to show the parameters. Brill !!!
  4. miso

    miso Guest

    I wonder if it was defective? Maybe it latched up.

    Otherwise, can you just hyperterminal to it and play around?
  5. miso

    miso Guest

    Actually, I need the Nissan/Infinti proprietary connector. Maybe a
    converter exists, but the damn SEO brings up catalytic converters when I
    do a search.
  6. miso

    miso Guest

    Well close. The Infiniti socket is 16 pins and so is standard ODBII. But
    this is a 14 to 16 pin adapter.

    And I thought only Apple uses GD proprietary connectors.

    The shop manual calls the ODBII scanner the GST (general scanner tool),
    just to make the manual harder to read I suppose.

    BTW, if you never did it, for like $20 or so, there are websites that
    let you download the official manuals. I suppose there are pirated
    manuals as well, but $20 seems fair considering what cars cost. You get
    a one day subscription to the service. it is really intended for repair
  7. josephkk

    josephkk Guest

    There is something weird about this, a PIC eating enough power to flatten
    a 12 V, 50 Ah or more battery in a few hours??? Hot enough to melt the
    case??? Where in hell is all that energy going?

  8. Charlie+

    Charlie+ Guest

    I have had one of these clone ELM bluetooth units for about a year 1.5
    version, no signs at all of overheating, gets slightly warm in use as
    you wd expect, I dont leave it plugged in doing nothing though....!
    Maybe OP has been unlucky in his units, but it seems to be a known
    problem, look on Amazon comments etc.
  9. josephkk

    josephkk Guest

    Bwahahahahah. Large companies have been using proprietary connectors
    since there were connectors, well over 100 years. How could you possibly
    be that naive?
  10. josephkk

    josephkk Guest

    This is on the OBD2 connector, which does not depend on the ignition
    switch position. Please pay attention properly.

  11. linnix

    linnix Guest

    It's just bad designs/programmers. Poorly design products can kill any battery. Don't they know about low-power/idle/standby modes? Perhaps they do and will be ready to sell you an upgrade with a premium price.
  12. tm

    tm Guest

    The 12 volts on the ODB2 connector is directly to the battery. It is on all
    the time.
  13. linnix

    linnix Guest

    And they know nothing about activity timer? All smartphones are connected to the batteries all the time, but not on all the time.
  14. Guest

    The ECU which they talk to isn't on unless you turn the key

    OBD2 connector has KL30, the ECU wake-up/shut-down based on KL15

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