S7-400H EXTF LED in one PLC is always ON!

Dear Experts,

we have commissioned a S7-400H station CPU 417-5H. Here we find a situation where all the components in the Profinet network are OK and PLC 1 is good condition, which means no fault LED is ON. But the PLC 2 is in faulty condition, the EXTF LED is ON. we have already tried the following actions but without any luck.

1. Restart of PLC2 (both warm and cold)
2. MRES on PLC2
3. Power OFF PLC2 and remove the CPU moudle out of Rack and then after 2 minutes connect it back to rack and switch the power ON. 
4. cross verified the firmware versions. they are the same V6.0.3.
5. Interchanged Master and Standby status which means initially PLC1 was master and PLC2 was standby, but later it was changed to PLC1->standby and PLC2->Master.

Attached also the online view of both the PLCs and their module information.

Any suggesstion as to how to proceed further is highly appreciated. 

Thanks and cheers

Santhosh

Hello santhosh;

You seem to have already done many tests and evaluations to determine the source of the EXTF LED fault signal.

What you need to do now is ask the CPU's operating system what is bothering it. Double-click on the red cross covering the stand-by CPU, in the online view of the HWConfig editor that you show.

This will open the diagnostic buffer of that CPU, and show all event messages logged by the OS, including faults. You should find messages related to this EXTF fault that will give you more explanations.

If you cannot understand the source of the problem from the diagnostic buffer, save the messages and post them here so we can help you more.

Hope this helps,

Daniel Chartier

Hallo daniel,

yes i will do that. Will post the entries of the diagnostic buffer. 

Cheers

Santhosh

Daniel,

as promised, here is the diagnose buffer file. Bear in mind i had performed master/standby switchover, complete restart of PLCs, so, so. 

I could not find any entry that would suggest this behaviour. Probably a fresh pairs of eyes catches somethings. 

thanks in advance.

Regards

Santhosh

hi,

I think this is communication fault from external i/o nodes.

Any BF led in i/o racks or in nodes?

check the communication.

Hello Santhosh,

I can't see further messages after your last attempt to put CPUs in redundant mode.

Anyhow, please check status of analog output module starting with address 724. Try to check it online as in the attached picture in your 1st post. Make sure it has no red signs.

Please, also check the settings of OB85 in HW configuration.

I recommend to limit the calling of OB85 to only for incoming and outgoing events.

Regards,

H-H

Hi

If address 724 belong to ANALOG module, any open loop on one of the channels, also will initiate

EXTF LED. You can check the IO module in the HW by clicking it and check channel wise healthiness.

Regards,

Vijay

Hi all,

we have resolved this issue. The root cause for one EXTF LED always on in PLC was due to the fact of Buffer battery monitoring. After replacing the buffer battery, the EXTF LED became dark. And everybody is HAPPY again. 

The buffer battery monitoring had been enabled and due to other messages in the PLC buffer it was not dectable earlier. 

As the diagnosis was remotely, we were challenged with hardships and led to extended time for resolving the issue. 

I hope this enlightens others. :)

Cheers 

Santhosh