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Thread: OBD Android OBD Application

  1. #1
    Newbie
    Join Date
    Aug 2013
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    1

    OBD Android OBD Application

    Hi guys,
    I have been developing an OBD-II app for the Android platform and I am running into a few problems. I have been able to test my applications on a few General Motors vehicles and they work just fine. But when I use it on Ford or Chrysler vehicles it does not seem to work.
    My application is fairly simple and works like this
    1. Sends PID request to ECU
    2. ECU sends data back to Android device
    3. Android app parses data and displays to screen

    I know that the OBD-II standard is supposed to be standard for all American made vehicles, but what I don't understand is why it works on some cars but not others. Are there different ways to present the PID requests for different vehicles? How are the requests handled in the different protocols of OBD-II??

  2. #2
    Maximum Bitrate
    Join Date
    May 2012
    Location
    Grandville, MI
    Posts
    646
    My understanding is that it may depend on the interface you are using. There might be timing issues and ODBII was not really as standardized as you might think when it first came out. I THOUGHT however that around 2005 all vehicles were supposed to be standardized on a common CAN bus protocol with some ID's and such preset but much is left to be OEM specific.

    You should be able to get things like speed, temp, o2 sensors, trouble codes, MAF, MAP, and some other standard sensors but beyond that depends on the vehicle you are reading. There are a bunch of different ODBII "standards" that came out before CAN was supposed to standardize everything.

    You can always put another ODBII scanner on your vehicle and track whats going on from a laptop or something to debug your software and see what is going on.

  3. #3
    Constant Bitrate
    Join Date
    Sep 2009
    Posts
    176
    which interface tool are you using? are you sure that you reset the protocol to auto? the PID request should be the same regardless of protocol. CAN-Bus vehicles have a lot of additional commands that you can peform with an ELM327 compatible chip, but they shouldn't be necessary for basic PID stuff like coolant temp, RPM, etc.

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