Running indication J1939 error

Ned 10 months ago in IQANdesign updated by Nick Pridham 10 months ago 3

Dear all,

Let me explain the problem and I hope someone could give me an idea how to fix it.

I have a transmission that goes to force neutral with no obvious reasons.

Attached is two picture of CAN trace on the bus.

FF20 is sent from our controller to the transmission and FF23 is what I get from the transmission.

As you can see for some reason the all bytes are changing to Fs what may cause this behavior.

In the controllers Log I see "running indication J1939 error" and althoug I am not 100% sure I believe this is relatet to the listed above. Can someone explain what this error stands for ?

Thank you in advance, all support will be appreciated.

I have had this problem on a couple  of different transmission applications.

FF is J1939 convention for unused bits and so if some FF20 packets are populated with data and some not then perhaps check the electrical design to see if there is a chance of physical faults causing dropped packets.

Double check the FNR signals in the application code. Some of the transmission controllers have very low fault tolerance when shifting between FNR contacts and small delays can cause timeouts and thereby forced neutral. Are you controlling the FNR value via a state machine ?


I don`t use state machine for the FNR values, the signals are independent and go directly to the JPINs.

We will double check the wires. I will test also different transmit rate, my colleagues suggest that this may cause the JFOUT to fail. In any case I`ll let all know when the problem is fixed and how we did it.

Ok so a good idea is maybe to run a trace on the FNR contacts and just check that a system sample without any direction signal at all is transmitted due to the FNR lever being in transition between contacts.  ZF is very sensitive in this area but very stable and reliable when you get the timings right.