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Thread: ODB-II Splitter

  1. #11
    Constant Bitrate joeyoravec's Avatar
    Join Date
    Oct 2005
    Livonia, MI
    Quote Originally Posted by aviator79 View Post
    Please help me figure out how to do this. I have a mazdaspeed6 with a dashhawk.
    I wouldn't bother sniffing the DashHAWK -- on Mazda they just use generic OBD2. You can buy the standards for about $50 (see here). No reverse engineering required. Between that and the manual for your OBD2 tool you should be able to recreate everything that the DashHAWK does.

  2. #12
    Join Date
    Oct 2007
    Well actually the MS6 (MS3/CX7) has very specific Pids that only the dashhawk can read. The programer that used to work on it worked with us to make this happen. See DH forums. This is no general mazda or even just a mazda6. The speed6 is completely different. Different ECU to begin with. It is a MZR DISI engine, turbo awd.

    So, Im looking to use the DH for uvwxyz
    AFR (MS6 has OEM wideband)

    and carputer for cool stuff not related to tuning like MPG and trip and then extras like coolant temp ect. Stuff that I think are more standard PIDS that any software could read. I know im not making sense but I hope to figure this out. Just need some assistance to get the ball rolling. I need to understand more about this stiffing and then start testing it out.

  3. #13
    Constant Bitrate joeyoravec's Avatar
    Join Date
    Oct 2005
    Livonia, MI
    The ones that you mentioned (boost, afr, mpg) are derived, calculated, or estimated from OBD2. I had forgotten about the 3 or 4 enhanced parameters on DashHAWK including wastegate duty cycle; some but not many. Of course I took a look at it when developing DashDAQ ( but I didn't see anything special. In contrast the DashDAQ reads a ton of enhanced PIDs. You can see the mazdaspeed forum where people post comparisons.

    In general on the speed6 the DashHAWK uses the same plain-old obd2 available to everybody but processes/computes the data in some unique ways to come up with things MPG. If you were writing your own software you could do the same based on public information.

  4. #14
    Variable Bitrate
    Join Date
    Oct 2008
    If your car supports the wideband O2 pids 24-2B or 34-3B you can see the equivalence ratio here. 1 equals lambda 1 = AFR 14.64.
    If your car supports the Actual load value pid 43 then you can see the boost here. 100% is atmospheric pressure. 200% is 1 bar boost, etc. This value is calculated by the ecu.

  5. #15
    Low Bitrate 2009Prius's Avatar
    Join Date
    Sep 2010

    Question OBD split cable?

    Quote Originally Posted by joeyoravec View Post
    But I would caution you that each device has a network address to communicate, including the scantool. You can't just plug in two tools like you describe and expect them to work perfectly -- they will conflict if they use the same address. Usually when people use a splitters they're "sniffing" the network to reverse engineer the network messages. In that situation they're passively monitoring the traffic and there would be no address conflict.
    Quote Originally Posted by Lukeyson View Post
    That OBD2Cables splitter works perfectly. I use it all the time on CAN and ISO9141.

    It's dead set easy to sniff traffic from another tool. I've sent messages with an ELM, Joey's Mongoose ISO/CAN, an IDS, a WDS and an FMP (Last 3 are Ford Dealer Tools) and have been able to sniff messages on CAN with 100% success, and ISO with a fraction less success, both with either the ELM327 or Mongoose. The ISO issues have less to do with addressing and more to do with Ford not conforming to ISO perfectly.

    For ELM sniffing just using Hyperterm and a mix of filters (mainly to limit broadcast traffic on CAN) and the atma command works just fine.

    For J2534 sniffing you might be able to use the Drewtech software tool (I struggled with it but didn't spend that much time on it) or alternatively go for another tool I use quite a lot called IPSecMsgMon - it's a part of the Cardix SDK - and it's helped me do a range of things, and is just about the most useful reverse engineering J2534 tool I've come across.

    I have a ScanGauge connected to my 2009 Prius. I am considering adding an OBD-USB adapter to send data to a laptop. I saw this split cable on amazon:

    How do I find out the network address of each device? Especially OBD-USB adapters - can the address be changed by software? Thanks!

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