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Some questions to community

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  • Some questions to community

    Hi all.

    Iím a novice in OBD2. I have spent a lot of time to exploring the internet and the information I have found is still confusing me. Thus, I have some questions to community.

    First. As I understand to communicate with ECU I shall use one of the ISO or SAE protocols. Looking through those protocols, I am suspecting that they are only for transportation purpose. The real commands and data should be provided by another way, probably using ALDL protocol. Is somebody can clarify the situation?

    Second. If I will have any ECU on my table, can I connect it to my computer for testing purpose? Will it work apart of car, without sensors? What do I need more for that task?

    Third. Is it possible control the car devices via OBD? I mean can I send a command to start engine using OBD? If not, how can I do it?

  • #2
    Originally posted by Taurus
    Third. Is it possible control the car devices via OBD? I mean can I send a command to start engine using OBD? If not, how can I do it?
    OBD-II turns on when you turn the key to the "ON" position. so no you cant start your car via obd-ii port because its not on unless your turn the key on. it's the same as what came first, chicken or the egg.
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    • #3
      If you could turn your car on, some one would sell a device lijke the Tek 2 that you plug up to an OBD-II car then start it and drive it off like you owned it.
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      • #4
        Straight up: OBD-II is an ECM access protocol, meaning that it is a standard for interfacing with your car's existing control computer. It doesn't have any control over your computer per se, BUT you can send commands to the computer through it. That being said, it may be a bit more obvious why it can't be used to start a car. The car must be started (or at least the key forward in power position) in order for the computer to be active, and pay attention to the OBD-II (On Board Diagnostics) interface. Cool?
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        • #5
          Alot of newer vehicles are starting to use CAN and LIN standards for control of non-powertrain functions like locks, windows, lighting, antitheft, etc.On late model GM vehicles I believe it is possible to start the vehicle via the CAN bus.As far as your other question, The SAE J-1850(vpw and pwm) and ISO-9141 are just hardware layers, the actual communication protocol(SAE J-1979) is the same in all.