Siemens Fault 0a7991 !!better!! [FAST]

Unlike critical hardware failures or short circuits, this code is technically classified as an , meaning it indicates a pending automated routine. However, it will actively prevent normal operation or motor startup until the drive successfully completes its internal measurements or the configuration sequence is properly terminated.

This code is not simply a “stop” signal; it is a sophisticated protective response from the drive’s internal monitoring system. If you are seeing 0A7991 on your Siemens SINAMICS G120, S120, G130, or G150 drive, you are dealing with a critical torque/speed deviation or a condition.

Run a short ramp. If speed remains near zero while torque climbs to p2175 , the fault is legitimate – mechanical block.

This comprehensive technical guide breaks down why this alarm occurs across Siemens SINAMICS drives, how to complete or bypass it, and how to resolve common communication locks. Root Causes of Alarm A07991 siemens fault 0a7991

If you are testing the machine locally without a network connection, set parameter p2030 = 0 (No Protocol) to tell the drive not to look for an active fieldbus line. Perform a RAM-to-ROM save, cycle the 24V control power, and the secondary communication error will drop out.

Once completed, the drive automatically resets parameter p1900 back to 0 (Inhibited), and alarm A07991 will clear by itself.

Based on common Siemens drive faults, you are likely looking for Unlike critical hardware failures or short circuits, this

: While this alarm is active—especially if a rotating measurement is selected—you may be unable to save parameter assignments to the ROM until the process finishes. Common Troubleshooting Steps

| Product Series | Model Examples | Applicable Manual Reference | |:---|:---|:---| | | G120, G120C, G120X, G120XA | Siemens G120 manual (A07991) | | SINAMICS V90 | V90 Servo Drive | SINAMICS V90 Operating Instructions | | SINAMICS S120 | S120 Servo Drive | SINAMICS S120 Commissioning Manual | | Other SINAMICS | G110M, G120P, G115D | Various SINAMICS documentation |

Compare the installed modules against the configured modules in TIA Portal: If you are seeing 0A7991 on your Siemens

Follow these three approaches depending on whether you want to the motor identification or deactivate it temporarily.

This alarm frequently appears alongside , which indicates a communication timeout with a PLC.

Locate parameter and adjust its data value back to 0 (Inhibited) . Ensure parameter p1910 is also adjusted back to 0 .

Although the exact cause may vary depending on the device, here are some potential reasons for the fault: