0a7991 [2021] - Siemens Fault

During the initial setup of a new drive, the control unit automatically activates the motor data identification function to ensure optimal performance and protection. As a result, A7991 appears on the control panel.

: If testing the drive standalone, set p2030 = 0 (No protocol) and perform a "RAM to ROM" save. Technical Summary Table Default/Action Description p1900 Set to 0 Disables the motor identification routine. p0971 Set to 1

To minimize the occurrence of the Siemens fault code 0A7991:

By understanding the typical causes—faulty modules, loose connections, configuration mismatches, or wiring shorts—and following the step-by-step diagnostics outlined in this guide, you can minimize downtime. Always remember to check the diagnostic buffer first, verify the hardware online, and keep OB 122 in your program as a safety net. siemens fault 0a7991

If you are reading this, chances are your Siemens drive or automation system has halted, and you are staring at the cryptic code on your operator panel or HMI.

It is very common for A07991 to appear alongside the fieldbus interface alarm . This happens because an incomplete commissioning file prevents the VFD from organizing its active cyclic process words with the upstream master controller.

Ensure your logic program sends a standard hex control word like 047E or 0400 down to the first data word of your cyclic telegram. This flips bit 10 to a high state, letting the drive know that a master controller is successfully supervising the bus. During the initial setup of a new drive,

When encountering a specific fault code like "0a7991", it's crucial to consider the context in which you're seeing this code. Here are some general steps you might take to troubleshoot or understand this fault:

When both occur simultaneously:

The primary cause of this fault lies in the drive's parameter settings. Specifically, the alarm is triggered when the following parameters are not set to zero: If you are reading this, chances are your

The Siemens fault code (often searched as 0a7991 ) specifically indicates that Motor Data Identification is activated . This is not a critical equipment failure but rather a status alarm triggered during the commissioning or configuration phase of Siemens SINAMICS drives , such as the G120, G120C, and G150 series. Understanding Alarm A07991

Open your active commissioning folder and explicitly trigger a RAM-to-ROM copy ( p0971 = 1 ) . If you bypass this save, the alarm will reappear the next time the mains power disconnects.

To clear this alarm and enable the drive for normal operation, you must either complete the identification routine or manually deactivate it. :

Siemens drives are robust, but they rely on precise communication between their internal and external components. Fault 0A7991 is a signal that this communication chain has been broken. By methodically checking your firmware, cables, and configuration, you can usually isolate the problem quickly.