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
Verify the nSubType value against the documentation for the specific parent item type where the child is being created.
- 2
Ensure the nSubType is appropriate for the itemType of the parent node to which the child is being added.
- 3
Review 'ITcSmTreeItem Item Types' (page 39) and 'ITcSmTreeItem Item Sub Types' (page 41) for valid combinations and dependencies.
Verified technical data. Last updated: March 2026
Related Faults
Source: Beckhoff TwinCAT 2 Automation Interface