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Topic: CAN bus issue on heavy truck (Read 3799 times) previous topic - next topic

alexstefanssa

Hi all,

I had this posted in the Home automation and network objects earlier. Just realized it was the wrong place for it so I'm reposting it here.

I am trying to connect to the CAN bus of a heavy truck via the 24v OBD2 port.
The CAN lines, ground and 24v are the only pins in the connector.
I am using an mcp2515 board, an Arduino UNO and the library by
Cory J Fowler(https://github.com/coryjfowler/MCP_CAN_lib).
I have confirmed it working on another vehicle, successfully receiving data.

On the vehicle that worked, the voltage difference across the can lines is 0.3v, which makes sense based on what I read online.

On my truck, the voltage difference between the 2 lines is 0v, the difference between each of them and ground is 2.45v, and the resistance across the lines is 120 ohm with the battery removed.
These are not consistent with what I managed to find online, and my setup is not working. Tried both with and without the terminating resistor on the mcp2515 board, both at 250k and 500k baud rate.

The truck works fine, and there are no issues reported in the instrument cluster.

I'm running out of ideas and would appreciate any input or advice.

Many thanks!

UKHeliBob

Quote
I had this posted in the Home automation and network objects earlier. Just realized it was the wrong place for it so I'm reposting it here.
The other thread has been deleted
Please do not send me PMs asking for help.  Post in the forum then everyone will benefit from seeing the questions and answers.

gerrikoio

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The truck works fine, and there are no issues reported in the instrument cluster.
Sounds like the truck manufacturer use their own protocols. What make of truck is it. Maybe then others could confirm this.

alexstefanssa

It's a Renault Range. Being part of the Volvo group, I would have expected it to follow the fms standard and adhere to j1939. The only pins wired into the OBD2 port are the ground, 24v and 6 and 14 for j1939

cassf1

Maybe try adding another 120 ohm resistor across the can wires so you have 60 ohms. 

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