E_ACCESSDENIED

Access Denied

Beckhoff · TwinCAT 2 Automation Interface

What does E_ACCESSDENIED mean?

The operation failed due to insufficient permissions or a locked resource. This occurs if the current document in the system manager instance is locked (e.g., when calling NewConfiguration() or OpenConfiguration()) because a reference to the system manager's object or a tree element is open. For DeleteChild(), it indicates that deleting the child item is not allowed due to protection or operational constraints.

Common Causes

  • Attempted access to a protected function or parameter without proper credentials.
  • User role or privilege level does not permit the requested operation.
  • Security lockout due to repeated failed authentication attempts.
  • Configuration error in access control lists (ACLs).
  • Attempting to modify a read-only parameter (e.g., P3-0).

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Close any open references to the TwinCAT System Manager object or any of its tree elements.

  2. 2

    Verify the TwinCAT configuration is in a modifiable state (e.g., Configuration Mode, not Runtime).

  3. 3

    Check user permissions in the operating system and TwinCAT security settings to ensure write access.

  4. 4

    Ensure the specific child item is not protected or actively in use by another TwinCAT process before attempting to delete it.

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Verified technical data. Last updated: March 2026

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Source: Beckhoff TwinCAT 2 Automation Interface