Siemens Fault 0a7991 Best -

A hidden gem: 0A7991 frequently appears after a firmware update or when using an older Starter/TIA Portal version.

Verify that the "Tipp" (Input/Output) times are consistent across all nodes in the synchronous group. 4. Analyze the Diagnostic Buffer The TIA Portal Diagnostic Buffer is your best friend. Go to . Read the entries immediately preceding the 0A7991 fault. siemens fault 0a7991 best