S7-400 Diagnostic Buffer

hi every body
we have a S7-400 (S7-414H) PLC that controls the comprossor.
It has changed it's mode from RUN to DEFECTIVE,and diagnostic buffer showes this message:
memory test error in internal memory
No relevance for user (Z1): f1bc
Previous operating mode: RUN (redundant mode)
Requested operating mode: DEFECTIVE
Event occurred in the standby CPU in rack 1
Internal error, Incoming event

Please help me to find out the cause of the problem and give me the relevant solution to solve the problem.

With the best regards

Hello Mehdi;
From the contents of the diagnostic buffer, you are using 2 S7-414H CPUs in redundant mode; the stand-by CPU (in Rack 1) has gone in Defective mode, because of an internal RAM test.
Here is what Siemens says about Single//Defective modes:




Basically, if you cannot download your original program to the faulty CPU and estart it, you may have to have it repaired or replaced (sorry I don't have better news...).
For more info, please download the pdf manual on S7-400H CPUs from Siemes' website:

"Automation System S7-400H Fault-tolerant Systems"​

Hope this helps,​

Daniel Chartier​

hi dear Danielthank you for your information it's help me.
as you mentioned the stand by PLC(S7-414H) has gone to defective Mode,i remove the battreis and turn it off.after a while i turn it on and try to download the program on it but i couldn't.
i changed the defective PLC,now every thing is OK.
but you know i want to know what's the meaning of this code:
f1bc ,that i read it at diagnostic buffer.(at diagnostic buffer help mentioned No relevance for user ) i check the siemens Manual and Website to dwanload some thing about it but untill
now i'm not succeed.
anyway thanks for everything.
take care.

Hello Mehdi;

When I have seen this type of message:

No relevance for user (Z1): f1bc

Click to expand...

I have found that only Tech Support can (sometimes) give me more information. I have never found accessible info on these messages.

If you really need to have further info on the subject, I suggest you contact Siemens (you will be asked for the contents of the diagnostic buffer at some point if yopu require repairs or replacement of the defective controller anyway).
Hope this helps,
Daniel Chartier