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I develop a CAN-BUS receiver (logger) with an ESP32 and CAN-BUS transceiver.

The CAN-BUS transceiver modules which I found and bought have both 120 Ohm termination resistors. But the CAN-BUS to which I want to connect this (in a modern motorcycle) is already terminated on both ends. I want to connect my device to the CAN-BUS service connector (like an OBD2 ELM327 adapter).

Do I have to remove the resistors from these modules to make sure the bus is only terminated on both ends?

Or do I have to keep these resistors to make sure the transceiver modules work correctly?

Is it possible that the CAN-BUS or any device on the bus will be damaged if I don't remove the resistor because the load is too high?

I bought several of those modules and I can do "try and error" if necessary.

Here are two pictures of those modules: CJMCU-1051 CJMCU-230

A little edit after a long time: I didn't upvote any answers because they are more recommendations than answers. I used the modules like they are including the resistors and for me that worked. But I used that in my bike for all together maybe only 10h and then I didn't do anything with this anymore. So for me and with my bike it works including resistors. But that is obviously no general answer to my question. My answer would be now: just try ;)

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    \$\begingroup\$ In theory you should remove the termination from the stub. In practice, CAN tends to not be very picky with extra termination on stubs, though this will depend on baudrate. At baudrates <500kbps the extra termination is unlikely to matter. It is more picky about missing termination. \$\endgroup\$
    – Lundin
    Commented Sep 20, 2019 at 13:45
  • \$\begingroup\$ Thanks, in my case it's 500kbps. Is it possible that the extra resistor creates problems because of the extra load (more current)? \$\endgroup\$
    – Edgar
    Commented Sep 21, 2019 at 0:17
  • \$\begingroup\$ You are asking if you should remove extra termination resistors on your module. The only correct answer is, yes you should, because you can't add more terminations to a bus or it might stop working. And the answers make that clear. Please accept such an answer. \$\endgroup\$
    – Justme
    Commented Jul 24, 2022 at 7:42

2 Answers 2

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As long as the (long) CAN Bus is terminated at both ends it should work providing the stub connecting your board to it is fairly short. So remove the termination from your board.

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You need one resistor at each end of the bus.

Diagram of CAN-Bus

Image source: KMP Drivetrain Solutions - Practical tips: CAN-Bus

Every other resistor could be removed.

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