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Thread: Mongoose & Opel Astra H 2007 CAN bus

  1. #1
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    Mongoose & Opel Astra H 2007 CAN bus

    Have been browsing through the forums for quite a while and finally decided to post something...
    I've got Opel Astra H 2007, and my carpc installation project is really stuck on planning stage due to the fact that the factory display bezel is definitely the best place for the monitor, however removing factory screen will mean loosing a hell of a bunch of vital info (i.e. climate control indicators, factory radio data & boardcomputer).
    Not so much info available on the net about Opel, however based on some experience of other Opel owners here in Russia there's an idea that factory screen data is transferred via Medium Speed CAN, also understood that this info is Opel-specific (or maybe some GM standards?) and not falling under generic OBD-II.
    Which scanner would be needed to scan medium-speed CAN traffic? Would ELM327-based tool be enough or something more advanced will be needed? And, finally if Mongoose GM will work with Opel (I guess Drewtech will not guarantee this, so I mean if anyone did try)?

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    Constant Bitrate joeyoravec's Avatar
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    Quote Originally Posted by leman View Post
    ...factory screen data is transferred via Medium Speed CAN, also understood that this info is Opel-specific (or maybe some GM standards?) and not falling under generic OBD-II.
    Might be. Sometimes they have a separate network for things like that, but bring it out to the OBD2 connector for diagnostics. Get a wiring diagram and figure out how the network is laid out.

    You could just as easily compute some of those things from the ECM. Range is the % fuel left in tank versus average fuel economy. Instantaneous consumption is based on the injector flow rate. The display isn't doing anything too crazy. It's more a matter of knowing how to read the data out of the ECM if you're going to write custom software.

    Quote Originally Posted by leman View Post
    Which scanner would be needed to scan medium-speed CAN traffic? Would ELM327-based tool be enough or something more advanced will be needed? And, finally if Mongoose GM will work with Opel (I guess Drewtech will not guarantee this, so I mean if anyone did try)?
    You might group CAN into three variants.

    1. High speed (500kb) two-wire CAN on pins 6 & 14. Typically used for Generic OBD2. Of course Mongoose GM can do this, but they don't sell Opel in the USA so I've never tried one.
    2. Medium speed (up to 250kb) two-wire CAN. Different name but only the baudrate and pins (typically 3 & 11) are different. Since Mongoose GM only does CAN on 6 & 14 you'd need to reroute the pins, connect at a lower baudrate, and start hacking.
    3. Low speed singlewire CAN. It's still called CAN but electrically it's totally different. Mongoose GM doesn't do that one (yet).


    Hope that answers your question.

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    Thanks for reponse

    Quote Originally Posted by joeyoravec View Post
    You could just as easily compute some of those things from the ECM.
    Yes, board computer info is not an issue, so the main problem is climate control and factory radio data. Guess I'll have to dig into TIS for wiring diagrams to check the network structure.

    From what you say about high-speed and medium-speed CAN, I understand that only baudrate is different - does that mean that any OBD-II scanning tool (i.e. ELM-327 based) should do both CAN types after connecting to other pins or that's an option for Mongoose GM and more advanced tools only? Getting ELM327 in Russia is MUCH easier than ordering smth (I mean Mongoose) from US...

    PS. Opel is sold in US as Saturn - not sure if they are indentical in terms of electronics, but Saturn Astra looks completely the same.

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    Constant Bitrate joeyoravec's Avatar
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    Quote Originally Posted by leman View Post
    From what you say about high-speed and medium-speed CAN, I understand that only baudrate is different - does that mean that any OBD-II scanning tool (i.e. ELM-327 based) should do both CAN types after connecting to other pins or that's an option for Mongoose GM and more advanced tools only? Getting ELM327 in Russia is MUCH easier than ordering smth (I mean Mongoose) from US...
    If anything I'd recommend you get tool like CarDAQ-Plus that lets you communicate on a single-wire CAN network too. Who knows; maybe you have one of those in addition to a medium speed network?

    I don't design or use the ELM. Therefore I have no idea if the ELM gives you control over the CAN datarate. Even if it gives you that control, I have no reason to trust it actually works for anything except normal OBD2. And after all that why invest the effort in writing software for the serial port when you could just use a PassThru driver DLL? Some guy has a fairly useful MsgMon utility that helps to reverse engineer CAN traffic. DrewTech has a free J2534-1 utility posted that lets you interact with the network. With all those resources you could probably get started on the real hacking a lot more quickly.

    Quote Originally Posted by leman View Post
    PS. Opel is sold in US as Saturn - not sure if they are indentical in terms of electronics, but Saturn Astra looks completely the same.
    Actually I drive two Fords. The non-USA versions are always quite similar. I don't think you'll have any surprises.

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    CarDAQ-Plus is great, but price-wise...

    I checked the wiring diagram in TIS and it looks like all info I need goes through mscan (though radio unit has also direct link to info display in parallel to communication through mscan). So I guess on this stage I'll have to decide on some ELM327-based scanner or Mongoose GM as a unit to start with.

    I'm not sure that I undestood this:
    And after all that why invest the effort in writing software for the serial port when you could just use a PassThru driver DLL? Some guy has a fairly useful MsgMon utility that helps to reverse engineer CAN traffic. DrewTech has a free J2534-1 utility posted that lets you interact with the network. With all those resources you could probably get started on the real hacking a lot more quickly.
    cause I'm actually real noob in programming (probably will need someone to do this part of stuff for me)

    I just wonder if getting some OBD-II scanner and wiring it to mscan pins in diagnostic lead to try to connect at lower speed is worth doing or I can damage the car electronics by doing this (I understand that Mongoose GM will work if connected to mscan leads, however the rewiring part would still be necessary since its original connector connects to hscan pins)?

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    Newbie Doka's Avatar
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    an idea that factory screen data is transferred via Medium Speed CAN, also understood that this info is Opel-specific (or maybe some GM standards?)
    IMHO, this work required great reverse ingeniring job: buy/find uC firmware (build-in-GID/CID), disassembly FW-code & restore specific CAN-protocol structure

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