CAN Bus Interpretation
 

Good afternoon everyone,
I’m currently working on a long-running project of a performance dash for the E53, although I’ve reached an impasse. According to what I see on the wiring diagram, I am missing the CAN pins on my OBD port(which are on 6 and 14) and have the K-Line pins (7 and 8) yet the wiring diagram says the can wires are YlwBlk and YlwBrw which are the colors of the wires in pin 7 and 8.
My CAN bus interpreter for my raspberry pi cannot read any data from 7 and 8 (which could be up to the setup of my CAN bus tool) which makes me think I don’t have CAN, yet BMW scanner 1.4 was giving me all kinds of messages about the CAN bus having been interrupted after I had hooked the interpreter up to it. This brings me to my questions.
1) Does the E53 (2005) have CAN bus?
2) Can it be interpreted in any way (I.e is it encrypted)?
3) What wires are 7 and 8 actually?
4) Is there a way for me to only connect to certain CAN busses (since I know all the different modules communicate using it, and I really only need the DME)?
Thanks in advance for any help!


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Are you sure about the wire colours on OBD2 port? Pins 7 and 8 should both be white/violet. Pin 7 is TXD2 diagnostic link to power train modules (engine and transmission) and pin 8 TXD to instrument cluster working as a gateway to K-bus modules. CAN high and low are those mentioned yellow/black and yellow/brown. That communication is only between engine ECU, transmission control unit, instrument cluster, ABS module and steering angle sensor.

https://xoutpost.com/attachments/x5-...us_systems.png

Yes, 2 of them (one for DME <-> AGS, one for DME <-> other modules), but not for diagnostics via ODB2.

Yes, Google "e46 CAN bus project". Messages are similar (if not the same) for BMWs of that era.

K-lines for diagnostics.

Heres the resources I have. I have a pinout from the internet and my OBDII pins
https://xoutpost.com/attachment.php?...1&d=1631312023
https://xoutpost.com/attachment.php?...1&d=1631312140

The generic OBD2 CAN pinout won't matter. That is a federal mandate for model year 2008 and newer. Even if your car was 2008 or newer the CAN pins on the OBD2 connector would not be directly tied to one of the CAN buses that the DME lives on - they would go to some gateway (body module, cluster, etc) and be filtered and/or altered by that gateway.

So my best bet is to tap straight into the YellowBlk and YllwBrw wires on the DME module itself. And at that point, how likely am I to end up permanently damaging something, such as the EEPROM?

Little to none, CAN is designed to be robust. You could absolutely interrupt bus traffic and set all sorts of codes, cause trans failsafe message, etc. by improper termination, shorting the bus or flooding it with high-priority messages.

You should make sure whatever device you connect is not terminated (since the bus is already terminated at both ends) and follow general CAN rules regarding wiring.

I'm guessing whatever hardware you use will live inside the car, so I'd tap in at the cluster or somewhere else inside. I would also look up pinouts on WDS and not rely on wire colors alone. You will want to use the bus that connects a number of modules, not the one specifically used for DME to AGS communication.

So what exactly do you mean by terminated? I’m not sure how I would be able to connect into the canbus wires without creating a termination. This add on board has a CAN H and CAN L screw down terminal block which I was using inline wire taps to get a signal for (plastic things with a metal insert that poke a hole in the side of the wire to give connection to another wire)
The only way I can think of to “avoid terminating” would be to cut the can bus wires, and run two wires to each of the boards terminals, so the connection between the modules is not being intercepted by the add on board, but is instead required to go through it


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Are you using a CAN bus module or chip or does the Raspberry Pie have built in CAN bus??

I’m using a CAN HAT called the waveshare RS485
It has a setup that is involved which I may have done incorrectly, but am unsure if that’s the direction you were going with the question.


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