While recording CAN SPN data on a Freightliner Cascadia J1939 bus I get expected reading for a while, then the SPN reads 0xFF for a few frames.

After it will read normal for a while then read 0xFF. Does anyone know what causes this? I use the same equipment and program on a Mack truck and the data reads normal all the time.

Good morning wsmith,

Are you getting any error messages? (e.g. serial sensor time out or not yet set?)
If you connect with DeTransfer, make sure the logger is in normal mode (You will be able to read the plain text when it is) and send the command P56=1 you will see the serial sensor port diagnostic output and how the data is being parsed.

This might give us some clues as to where things are going astray.

Cheers,
Roger

Good morning All,

It appears the CANGate and DT80 are working. The strange data appears to be an error message from the CAN system.

Cheers,
Roger