4012

Axis identifier not allowed

Beckhoff · TwinCAT 2 NC

What does 4012 mean?

An unacceptable value (outside the range of 1 to 255) has been used for an axis identifier, or the specified axis does not exist within the current system configuration. This parameter error prevents proper identification and control of the specified axis, leading to its inability to move or respond to commands.

Common Causes

  • Invalid axis number specified in the NC program or PLC command (outside 1-255).
  • Configuration parameter P4-01 ('Number of Axes') defining the total axes is incorrect or too low.
  • Attempting to access an axis that has not been defined or enabled in the NC configuration.
  • Mismatch between the configured axis count and the actual physical axes connected to the system.
  • Programming error in the HMI or PLC logic providing an out-of-range axis ID to the NC.

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    1. Review the NC program or PLC command that generated the error and adjust the axis identifier to a valid, configured axis (e.g., Axis 1, Axis 2).

  2. 2

    2. Check the NC configuration parameter P4-01 ('Number of Axes') to ensure it matches the physical and logical axis count.

  3. 3

    3. Verify the axis definitions in the NC setup (e.g., System Configuration menu > Axes) to confirm the specified axis exists and is enabled.

  4. 4

    4. Reload the NC configuration from a backup file to ensure proper axis definitions.

  5. 5

    5. Debug any external systems (e.g., HMI, SCADA) that send axis commands to ensure they use valid axis identifiers.

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Verified technical data. Last updated: March 2026

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