S7-300 with CP343-1 Comms Issue

[DJones183]

I have an S7-300 and an HMI. The HMI is the only device that talks over Profinet through the CP343-1 module. It's run fine for a couple of years and then earlier this week the CP343 had a red fault light. We replaced with a new CP343 and loaded the configuration but the HMI would not talk.

Now here's the weird part. When I go online with the PLC using my A2 adapter, the HMI starts working over the Profinet. As soon as I go offline, the communication stops. Siemens support was as lost as I am.

Any ideas?

 

[Lare]

CP343-1 uses MPI for communication to CPU.

If it works when you connect MPI programming cable, then failure is probably on MPI backplane side instead of CP343 card.

 

[DJones183]

CP343-1 uses MPI for communication to CPU.

If it works when you connect MPI programming cable, then failure is probably on MPI backplane side instead of CP343 card.

I believe that is what happened. I have been helping over the phone with a guy down there and just about an hour ago found out the CP343 isn't installed in the main rack, it's in a remote rack. He ended up finding the ProfiBus connector on the remote rack was loose and not screwed down. He's secured it and has now been able to remove his laptop and they are bringing the line up now.

Fingers crossed that fixes it.