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Thread: Doing more with OBD

  1. #1
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    Doing more with OBD

    I am really interested in figuring out what else can be done through ODB besides just reading codes and displaying engine statistics. In most cars, it has soo much more potential. How cool would it be able to integrate completely with all of the factory hardware, lights, sound system and buttons, keyfobs, steering wheel controls, cruise control etc. Thats what i am working on.

    So far in my 04 impala, i have figured out:
    *how to read evets including pressing any of the radio or steering wheel buttons door lock/unlock car power mode, doors opening and closing etc
    *control the text displayed on the factory radio. I don't have this perfected yet but i'm workong on it. In cars with text displays on the dash, we could control that too.
    *control the brightness of the dashboard and DIC lights. I really want to figure out how to control the main interior lights
    * control various things on the dashboard. :: plays with idea of temperature guage VU meter::
    *make the radio chime in several different ways
    *turn off the entire interior of the car while it is actually on (figured out this one by accident)

    If there is enough interest, it would be cool to put these things into a program or at least an API that could be used by other programs. I am pretty much limited to figuring out stuff for GM cars because thats all i have to play with. I know it is possible to control MUCH more and even things like the transmission etc because the Tech II the dealer uses can. This is just a start.

  2. #2
    MySQL Error scott_fx's Avatar
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    check out www.topdowntech.com i have a module that plugs into the obd-ii diagnostics port which allow me to recall my top speed and also roll my windows up or down with the factory keyfob/remote

    they also have a few other gadets that may spark some ideas


    this sounds really cool though, i'd love to see the potential of this project.
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  3. #3
    Newbie gabureiru.'s Avatar
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    I'm interested what equipment are you using?

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    I am using an elmscan 5 http://scantool.net/products/elmscan_5.htm .

    I chose it because its fairly cheap, has good documentation and can snoop communications over the bus.

  5. #5
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    The OBD standard doesn't let you do very much with the car. What you are tapping in to is the manufacturer specific functions that they have put into the car because they were required to put OBDII into it.

    Those vary by car, making it difficult to standardize functions. I'm sure your GM codes don't work for my VW and vice-versa.
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    I use the term OBD looseley because i don't really know what else to call it. I realize that these protocols are manufacturer specific and that it must be figured out for different cars. My aim is to figure out much of the proprietary protocols for GM cars with "class 2 data busses" only.

  7. #7
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    Unfortunately it's not going to be published anywhere unless you can beg/borrow/steal the info from an ex-GM (etc.) who actually programmed the subsystem.

    The easiest way to figure it out is to use a factory tool and a device like CarDAQ-Plus or Mongoose that can sniff the traffic on the bus. Reverse engineer the commands and see what is going on.

    It would be pretty cool to see that stuff documented on sourceforge, or the forum, or somewhere else. I'm sure a ton of people would love to mess with components on their vehicle.

  8. #8
    Raw Wave lostreception's Avatar
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    can you in turn read any data or is it encrypted etc

    for example can you scan all availible addresses for 123 (your milage being 123 miles) and then map to that output or is there much more involved
    for example id love to tap MPG (assuming its stored in the ECU)
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  9. #9
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    Quote Originally Posted by joeyoravec
    Unfortunately it's not going to be published anywhere unless you can beg/borrow/steal the info from an ex-GM (etc.) who actually programmed the subsystem.
    I have noticed. There are people out there who know but for the most part they guard the info like a national secret. They are making great amounts of money by selling expensive packages. I would like to change this and try to document some of the proprietary protocols openly.

    Quote Originally Posted by lostreception
    can you in turn read any data or is it encrypted etc

    for example can you scan all availible addresses for 123 (your milage being 123 miles) and then map to that output or is there much more involved
    for example id love to tap MPG (assuming its stored in the ECU)
    As far as i can tell, the only thing that is encrypted is the upload and download of new firmware to the ECU, BCM etc. Everything else doesn't seem to be.

    Its a slow process. I started out with this: http://www.hptuners.com/vpw.htm which gives me a vague idea of what the things on the bus are what. From there i have started to figure out simple messages like the one mentioned above. The problem with sniffing is that it is difficult to figure out commands that never occur naturally. Ther service manual helps a little too.

    From what i have been able to glean from various sources, MPG seem to be a figure calculated from the vehicle speed and fuel injector command. This info is available from the ECU. What year is your van? I'll see what i can figure out

    from the service manual
    Instantaneous Fuel Economy (INST)
    Instantaneous fuel economy is calculated as the ratio between the following values:

    IFE=Distance/Fuel
    Distance=The accumulated distance since last update
    Fuel=The accumulated fuel delivered since last update
    You cannot reset the IFE mode. The value of this mode is retained during ignition OFF.

  10. #10
    Raw Wave lostreception's Avatar
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    yea the van is dead at the moment needs anew engine etc
    its only OBDI it doesnt save mpg id have to calculate it
    i was more interested in my new vehicle but its non gm so its a totally different protocall
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