Electrics: 70: Diag issues - 1/2 of the car will not communicate

[Foxik]

Originally Posted by 4x4

This one will work Click

Thanks for the suggestion!

I got one dongle working ("We do it right because we do it thrice...").
SRS is now communicating. DIM and ABS are still silent... Even with the CAN jumped from DIM to OBD-II.
I tried to unplug DIM, to test ABS, but ABS is still silent.

I am suspicious of one of these modules, especially the ABS.
I will look on the CAN waveforms, I did save them on the scope. The CAN voltages are low, but the CAN still seems to work.
My current thoughts are that one of the CAN chips is faulty and brings the CAN voltage low.
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Update after analysing saved waveforms from the scope:
The CAN is moving from 0-1 V (Hi) and 0 - -1 V CAN LOW

the transceivers are
https://html.alldatasheet.com/html-p...6/A82C250.html
Both in the DIM and ABS modules.

The datasheet specifies that the output voltage should be like in traditional CAN - 2,5-3,5 V (Hi) and 2,5-1,5 V (Lo). Thus seeing voltages moving around 0 V, not 2,5 V, although the 2 V difference between CAN is OK can be the issue.
Funny enough - I am starting to think that these transceivers are so tolerant (according to the datasheet spec.) to voltage faults that they can communicate between themselves - thus I can see CAN coms, but the Dongle can not communicate, because it is looking and communicating in traditional CAN around 2,5 V.
We might be looking at a shot transceiver. Hopefully not dead driving logic - I can't bench test it (I think).

I will check the car with scope again, and I will try to narrow the fault to the exact module, so I can check it on the bench...