If a drive is powered down or undergoes a warm restart while an ID routine is selected but unexecuted, it can throw persistent or repeating alarms.
This guide provides an in-depth technical breakdown of fault A07991, explaining exactly what it means, why it appears, and the best step-by-step methods to resolve it safely and permanently. siemens fault 0a7991 best
Which are you using (e.g., S7-1500, SINAMICS S120)? If a drive is powered down or undergoes