When you implement the a J1939 ECU into your project you can see the status of the J1939 ECU in your code.

To monitor it you can use piece of code like this:

//J1939 status
xJ1939WatchDog := J1939_ECU.State <> J1939.ECUSTATE.OPERATIONAL; //J1939_ECU is name of ECU in J1939 Manager