Check your communication with the PLC. A08526 indicates the PLC is not sending the correct control word (bit 10 must be high).
(via PLC or local control). The drive will energize the motor (often making a whistling sound) for several seconds.
: Check for mechanical blockages, ensure the brake is releasing correctly, and verify that the motor cable connections are secure. Siemens SiePortal Troubleshooting Steps If you are still seeing "0a7991" on a specific display: Check the Source : Verify the code on the Siemens SiePortal or within the TIA Portal "Online & Diagnostics" view. Confirm the Hardware
You can resolve this alarm using one of two primary methods through the Siemens SiePortal Complete the Identification Process
To resolve the A07991 alarm, you must ensure the motor identification process is completed. Method 1: Perform the Motor ID Run (Recommended) siemens fault 0a7991
: 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
Ensure the motor is safe to run (especially if "Rotating Measurement" is selected). Run command
Apply a (start signal) to initiate the routine.
Restoring the drive to its default settings will also reactivate the motor identification function, causing the alarm to reappear. Check your communication with the PLC
Depending on how the Motor ID routine was configured, you may experience one of two behaviors:
No. It occurs on S7-300, S7-400, S7-1200, and S7-1500 systems, but the exact diagnostic text may differ. On S7-1500, it is often accompanied by a more descriptive text like "Module reports channel error."
: The motor will whistle or hum for roughly 10 to 30 seconds. Do not cancel or disrupt incoming line power.
: Ensure all hardware and motor parameters are correctly entered in the configuration. Run Motor Identification : Navigate to the commissioning folder. The drive will energize the motor (often making
Ensure the PLC is not triggering a re-identification command.
Disclaimer: This article is for informational purposes. Always follow your plant’s safety procedures and Siemens official manuals when working with live automation systems.
If you have tried all the above solutions and the alarm still persists, consider opening a case with Siemens Technical Support. Be ready to provide: