PEAK-System Forum

Hello folks, I'm investigating a random issue that affect a j1939 bus. From time to time the bus stop working properly, the bus load reach 95% and a sequence of error frames is broadcasted. Can anyone explain if is possible to get any clue on the issue decodic the error frames? If yes, how could I decode them?
Attached part of a trace where the error frames show up.
Any help is appreciated.

Hello,

You can always refer to the PEAK-Trace format description:

https://www.peak-system.com/produktcd/P ... Format.pdf

In your case, please look up format-version 2.0 (Page 112 of the document), which is used by PCAN-View.

Your trace shows form-errors, which do occur if the CAN-controller detects an invalid value
in of the CAN-Frames expected fields.

There are multiple possible causes for this, please check the following:

- Does the used bitrate match on all devices on the bus? (Also check the used sample-point)
- Is you CAN-Bus properly terminated? (120 Ohm on both bus ends, you should have ~60 Ohms between CAN-high and CAN-Low on the bus in an unpowered state)
- Check your cabling for possible damages


Please report back to us with your findings.

Best Regards

Marvin

Hello Marvin,
thanks for the quick response.
After several hours of investigation we did find the cause, it was a connection for a spare node, apparently well realized and properly capped, full of mud and moisture.
In certain conditions, not continuosly, the bus was reaching 95% load and voltage CANH-GND a value of 6.5V.
Hope this experience will help other people in their troubleshooting activities.
Regards.