Siemens Fault 0a7991 Best

The drive is operating in standalone I/O control mode, but bus parameters are active.

Depending on whether you want to complete the identification or bypass it, use one of the following methods: How can resolve the alarm Code 7991 and 8526 - SiePortal

💡 If your PLC cycle time is too high, consider moving non-critical logic to a different cyclic interrupt (OB) to prioritize the motion control communication. When to Contact Siemens Support

If the alarm does not clear after a successful ID run or power cycle, try these steps: Siemens SiePortalhttps://sieportal.siemens.com How can resolve the alarm Code 7991 and 8526 - SiePortal siemens fault 0a7991 best

For the best accuracy, run the motor ID when the motor is at ambient temperature.

: The motor data identification parameter ( p1900 ) was inadvertently altered during programming. The Three Best Solutions to Clear Alarm A07991 1. Perform a Motor Identification Routine (Recommended)

Understanding why this code appeared is the first step toward the best fix. Usually, it stems from one of the following: The drive is operating in standalone I/O control

Mismatched telegram settings between the PLC and the Drive.

Navigate to the commissioning menu in STARTER or Startdrive.

Alarm A07991 functions as an operational status flag. In the Siemens diagnostic naming convention, "A" stands for , meaning the drive will continue to run or stay ready, while "F" indicates a Fault that trips the unit instantly. : The motor data identification parameter ( p1900

A07991 rarely appears in total isolation. Technicians frequently encounter it alongside secondary industrial communication or state faults:

If you are running a rotating measurement (p1900=2), ensure the mechanical brake is physically opening. If you'd like to dive deeper, let me know: Which drive model are you using (G120, S120, etc.)? Are you using TIA Portal or a BOP/IOP panel?