we are facing a similair  problem on CPU 414-4H , EXTF and BUS2F  leds blink simultaneously then unit  shuts-down , there might be hard ward failure   but it seems difficult to locate the failed module , any one of you  could help   please

For further information i have attached the diagnostic buffer downloaded from CPU

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Split from About 414-4H CPU fault - INTF and EXTF lamps are flicking rapidly.

Hi Import-User-1,

Definitely, The PLC is faulty. The frequency of flashing will give u more idea of problems. Download the CPU manual for more details.

one more  step we have tried , the suspected CPU  was replaced by a new one  but problem  persists again , for your clear understanding  , I mention that there are  tow redundant CPU's are configured in the HW configuration but one is out off service , i wondered if that may affect unit operation 

thank you for your interest