How get information from OB86_Z23 where communication error occurred?

I would like to detect communication lose in my configuration. So I need some help in that. Could someone help me how to get information from OB86 temp variables? When I pull out ethernet connection from  IM 155-6PN ST  who is connected to CPU1510P-1 PN in diagnostic buffer next text

"Error: IO device failure - Data transfer fault (no frame received)

"

and 

"Error: IO device failure - IO device not found

From diagnostic buffer I know that communication error occurred between CPU and IM155 (IO device 1).

Looking at OB86, I had B#16#39 with B#16#CB:

From the HELP for this type of fault, it says:

OB86_z23 has a sequence (where the most left bit is the most significant 31 bit):

00001010 10000000 00000110 00000001

So if I have multiple IM 155 connected over scalance to my CPU, how could I get information from OB86_Z23 where communication error occurred, (for example, I want to know that communication error occurred between cpu and IO device_1) or is it a better way to use RALARM?

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Split from Identifying faulty module in rack from OB86.