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I'm trying to read the CAN-BUS via the OBD port with a PiCAN, it works fine for one of our cars. But for the other (a 2007 Mini One) I'm just getting the same frame repeated until the bus is apparently 97% congested:

can0  130   [5]  45 FF FD FF FF
can0  130   [5]  45 FF FD FF FF
can0  130   [5]  45 FF FD FF FF
can0  130   [5]  45 FF FD FF FF
can0  130   [5]  45 FF FD FF FF

Changing the bitrate just returns junk data, and it is listed here as supporting CAN 11bit 500kb anyway. Starting the engine, stopping the engine, nothing but this one frame...

If anyone has any ideas about what is going on they would be very much appreciated!

  • This may not be the best forum to ask this. As automotive service professionals we rarely actually deal with the CAN bus. We buy tools that take care of the communications for us. At most we have to figure out why the bus may be shorter or open. – vini_i Nov 25 '16 at 15:30
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The OBD port on some newer cars is connected to a 'gateway'. Sometimes it is a standalone device (like (VW) or sometimes it is in the instrument cluster or another CAN node.

This is because there can be multiple CAN buses in one vehicle.

It sounds like the BMWs is also connected to a gateway rather than directly connected to CAN Bus but i'll check this out and edit.

Depending on what information you would to access it would be best to connect directly to the twisted pair CAN Bus wires directly. For example if you want engine data connect to CAN wires that are known to connect to the engine ECU. The instrument cluster is usually a good place to start. Or find which device is the CAN gateway and you could access all of the CAN Buses.

You also have to make sure that all settings are correct such as the baud rate and wiring. I've never used the PiCAN but I've previously found that cheaper analysers tend to freeze and cause a bus off condition when there is a large number of IDs.

  • Looks like there is indeed a gateway. Apparently some people have managed to get through it, using the codes discussed there I did get a response but nothing useful. Time for the wirecutters! – RMc Nov 29 '16 at 12:48
  • Depending on what info I needed and how many buses I had to access I would build my own multiple channel CAN bus shield / interface. I have built my own 3 channel device but it is extremely over kill for what I need. The benefit is you only have to reverse engineer the raw CAN data for each bus rather than the gateway protocols which is usually some sort or request and receive type system. Downside being it wouldn't be plug and play – Terry Gould Nov 29 '16 at 14:00

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