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Tapping into CAN bus wires, what am I doing wrong?

Indicava Jan 28, 2018

  1. Indicava

    Indicava New Member

    I'm using a USB-to-CAN adapter to try and sniff CAN bus traffic on my 2015 Audi A3. Using an OBD-to-DB9 cable and the USB2CAN device I hooked up my laptop to the OBD port. Unsurprisingly I didn't see any traffic, except a constant "heartbeat" type message every second or so. This at least let know my basic setup was working.

    Next, I soldered a DB9 connector to two wires connected to clips like these and hooked the clips to the CAN pins on the OBD port. I got the same results as with the other cable telling me my wiring for CAN traffic was correct.

    Lastly I followed my car schematics, and spliced two wires which go into this connector on the left side of the trunk of my car. I chose this connector since it was easily accessible and since I saw two wires going into it which fit the color scheme for CAN Hi/Lo from both the schematics and others sites I found online. Eventually the finished result looked like this:


    However I am not seeing any traffic what so ever :( I did set the uplink baud rate to 100kbps as per information I found online and AUDI documentation (Comfort CAN bus).

    Any idea what I am missing?

    I have two theories:

    1. Maybe I don't have a good enough connection between the clips and the exposed wire. I know its hard to tell from the picture I uploaded but they do seem to clamp down on the copper wires. I felt uncomfortable fiddling with them anymore than that for fear of breaking/tearing them.

    2. These are the wrong wires. If someone out there has any experience with the wiring pins on the T17F connector, I would love to know if I understood the schematics correctly.

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