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Thread: OBD2 question

  1. #1
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    OBD2 question

    Hello I am new to all car stuff in general, but i am working on a project which my team hopes to use the OBD2 port as part of the project.

    I have been trying to figure out what type of information (besides diagnostic trouble codes) that the OBD2 can give. We are mainly looking for information such as the car is turned on and if a car door is open. Can this type of information be accessed through the OBD2 and how? Trying to do this for all the different OBD2 protocols and plan on using the ELM327 chip to interface with.

    Thanks

  2. #2
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    OBD is On-Board Diagnostics and is really for engine/emissions/transmission(emissions were the main objective).

    While you should be able to see that the engine is running by checking RPM's, I am not aware of any that will tell you the door is open unless it is a manufacturer specific PID - I know I do not have that available from the OBD2 port in my car

    I have a full gauge cluster ++ running from my OBD2 port at this time including speed, rpm, intake air temperature, left and right bank long term and short term fuel trims, o2 sensors for air/fuel ratio(left and right), knock retard, maf and map sensors, injector pulse width, throttle position sensor, wideband o2 sensor, and engine coolant temperature - and there are quite a few more available.

    I am not using the ELM327 though
    If anyone gives me a rev - I give them the Bird

  3. #3
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    Quote Originally Posted by wassi View Post
    Hello I am new to all car stuff in general, but i am working on a project which my team hopes to use the OBD2 port as part of the project.

    I have been trying to figure out what type of information (besides diagnostic trouble codes) that the OBD2 can give. We are mainly looking for information such as the car is turned on and if a car door is open. Can this type of information be accessed through the OBD2 and how? Trying to do this for all the different OBD2 protocols and plan on using the ELM327 chip to interface with.

    Thanks
    Wassi,

    If this is a student project, please send me a PM with your email. Our company sponsors student projects (you get free hardware, that is guaranteed to work -- unlike the ELM327 clones).

    Rick described one way to know that the engine is running. There is another way to do it using ElmScan 5.

    Depending on how old the car is, you may be able to capture and identify the messages that get sent when you open the door.

    Best regards,

    Vitaliy
    OBDLink MX: world's smallest, fastest, most advanced OBD/Bluetooth adapter with SW and MS CAN support. Read the review to learn more.
    Need to look up a diagnostic trouble code? Try the most up-to-date, free DTCsearch.com!

    You cannot send me a private message using this forum. Use my email instead: vitaliy[@]scantool.net.

  4. #4
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    Quote Originally Posted by Rick99TAWS6 View Post
    OBD is On-Board Diagnostics and is really for engine/emissions/transmission(emissions were the main objective).

    While you should be able to see that the engine is running by checking RPM's, I am not aware of any that will tell you the door is open unless it is a manufacturer specific PID - I know I do not have that available from the OBD2 port in my car

    I have a full gauge cluster ++ running from my OBD2 port at this time including speed, rpm, intake air temperature, left and right bank long term and short term fuel trims, o2 sensors for air/fuel ratio(left and right), knock retard, maf and map sensors, injector pulse width, throttle position sensor, wideband o2 sensor, and engine coolant temperature - and there are quite a few more available.

    I am not using the ELM327 though
    Can you eloborate on which PID in J1979 this is or do you just know your manufacturer specific PID?

  5. #5
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    I would suppose it depends on the car, really?

    E.g. for VAG cars (Volkswagen, Seat, Skoda, Audi, Lamborghini, Bugatti, Bentley), I know you can draw all kinds of information from it, but even more importantly, you can alter the way the car or certain aspects of the car behaves, e.g. if you'd wish the light on the car to stay on after you get out at night, and if so - which lights? , etc.

    I think the most interesting thing (in my mind) is what you can send the other way (to the car) rather than what it can tell you. At least on VAG cars, because they use the same software for pretty much every car, so you can enable "accessories and options" with the click of a mouse.

    Things like ignition can be taken from the RPM signal, as mentioned. You can also detect movement/standstill/speed (for navi - some OEMs use it to calculate the cars movements on a temporary signal loss), but things like "open door" doesn't pass through the OBDII on any car I've worked with. Instead, you'd be looking at something like getting a relay to act as a potential free switch, and mount that on the wire that runs to the ceiling lights from the car (not +12V or chassis/ground, but the wire that powers the bulbs when the door is open).

    Basically anything that can possibly generate a signal can be used.

  6. #6
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    Can you eloborate on which PID in J1979 this is or do you just know your manufacturer specific PID?

    It is actually in hardware/software I use for tuning GM LSx engines(HPTuners) along with the logging capabilities, but my understanding is that it is actually a calculated value which is requested by the GM PCM of the injector - so it is possible to see values over 100%(would indicate a need for bigger injectors if occurring regularly)
    If anyone gives me a rev - I give them the Bird

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