TSM_E_INVALIDITEMSUBTYPE

Invalid Item SubType for Creation

Beckhoff · TwinCAT 2 Automation Interface

What does TSM_E_INVALIDITEMSUBTYPE mean?

The provided nSubType parameter for creating a child item is invalid or not compatible with the parent item's type (0x98510003). The usable subType depends on the parent tree item's category; for example, a PLC Functionblock may only be added to a PLCFOLDER item, not a DEVICE item.

Common Causes

  • An attempt was made to create a TwinCAT item with an invalid sub-type.
  • Trying to instantiate a device object with incorrect attributes.
  • Incorrect configuration parameters for a specific sub-component type.

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Verify the nSubType value against the documentation for the specific parent item type where the child is being created.

  2. 2

    Ensure the nSubType is appropriate for the itemType of the parent node to which the child is being added.

  3. 3

    Review 'ITcSmTreeItem Item Types' (page 39) and 'ITcSmTreeItem Item Sub Types' (page 41) for valid combinations and dependencies.

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Verified technical data. Last updated: March 2026

Related Faults

Source: Beckhoff TwinCAT 2 Automation Interface