What causes Siemens SINUMERIK alarm 101001?

Normal control operation generated this status message. User action or program command triggered this notification. System configuration or commissioning activity produced this message. Machine data or parameter change created this notification.

How do I fix Siemens SINUMERIK alarm 101001?

1. Read the complete message text on the SINUMERIK screen — note any parameter values shown. 2. If action is required, follow the instructions in the message. 3. Acknowledge the message on the operator panel to continue operation. 4. Consult the Siemens SINUMERIK alarm documentation for message 101001 if clarification is needed. 5. If this message appears unexpectedly, review recent parameter or configuration changes.

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Siemens SINUMERIK Controller

PLC · Intermediate · 30-120 minutes

Alarm 101001

Siemens 840D 101001 - Cannot read PLC system status list !

Alarm 101001 indicates a communication failure between the NCK (Numerical Control Kernel) and the PLC system during startup or connection initialization. The NCK cannot access or read the PLC's system status list, which is required for normal operation. This typically points to communication bus errors, PLC initialization failures, or corrupted system data.

Siemens SINUMERIKPLCIntermediate30-120 minutes

101001

Siemens 840D 101001 - Cannot read PLC system status list !

Cannot read PLC system status list !

Root Cause Summary

Alarm 101001 indicates a communication failure between the NCK (Numerical Control Kernel) and the PLC system during startup or connection initialization. The NCK cannot access or read the PLC's system status list, which is required for normal operation. This typically points to communication bus errors, PLC initialization failures, or corrupted system data.

Safety

Refer to Siemens documentation
Ensure qualified technician performs repairs

Causes and Fixes

1
Perform a complete power cycle: Switch off main power, wait 30 seconds for all capacitors to discharge, then power on and observe boot sequence.
2
Check PLC diagnostics via HMI: Navigate to Commissioning > PLC > Diagnostics and verify PLC status shows 'RUN' without errors.
3
Review PLC boot time in STEP 7: Check CPU properties and increase PLC startup monitoring time if necessary (typically found in CPU properties > Startup).
Modifying PLC startup parameters requires STEP 7 authorization and may affect machine safety functions.
4
Verify PLC program integrity: Compare online PLC program with archived version and reload if corruption is suspected.

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