S7 CPU416-3 PLC 'STOP due to IO Error' fault

Hello DesignTech:

Good report basically.

But we need the complete diagnostic buffer readout (you seen to have saved the text file containing the buffer messages you included in your report) to help evaluate the situation. Please attached the text file on your next post.

One more thing: if you access the HWConfig editor in Online view, you can double-click on any fault icon (as you show on the CP 443-5 EXT in your report for example) and open the local diagnostic buffer of the particular module. It might be interesting to see if all CP 443-5 EXT showing a fault have similar entries in their buffer.

Hope this helps,

Daniel Chartier 

Hello DesignTech;

At first glance, you are right that the diagnostic buffer does not seem to point to a single source of problems on your system.

The only time I had faced a similar problem (loss of communication with multiple modules on the rack, I/O faults flooding the diagnostic buffer), the problem was found to be on the rack itself. If you happen to have a spare rack I would suggest you swap it in to your system, and insert all modules back in the same position they were on the original rack;  check whether issues are corrected by this intervention.

It turns out that on the faulty rack (that was a long time ago, so forgive the poor amount of details) some backplane pins had been twisted, probably during removing and re-inserting one module; the circular motion imparted to the module when inserting it probably caused 2 or more pins to be pushed out of position, and caused a short-circuit on the backplane. The CPU still was operational and reachable, but a number of consecutive modules after the short-circuit point were not available, and the diagnostic buffer filled with similar messages as you show (as far as I remember). I would then suggest that this be checked and corrected if it turns out to be the cause of the problem.

Hope this helps,

Daniel Chartier