Resolving SIMIT TIA Portal Project Openness Load Error

Problem Overview

SIMIT (Siemens Mechatronics Simulator) users attempting to import a TIA Portal project frequently encounter the following error dialog when selecting a project in the SIMIT project tree or running the PLCSIM coupler wizard:

The TIA project is possibly opened in a TIA instance, the project contains errors in TIA or some addon packages in TIA are missing.

The dialog is generated by the SIMIT-TIA coupling component (the SIMIT_COUPLER add-in used by the PLCSIM, S7-PLCSIM, NX-MCD, and TIA Openness bridge). It is a generic message that maps to one of three distinct root causes. Because the text does not indicate which branch fired, the technician has to test each path in order. The message has been reported on the following confirmed combinations:

The message text is a logical OR of three failure conditions. The coupling checks them in sequence and stops at the first one that matches, so the same dialog can be triggered by any of the three.

Root Cause Analysis

The SIMIT-TIA import path is built on top of the Siemens TIA Openness automation interface. Before the SIMIT coupler can read tags, blocks, and the project tree from a TIA project, the following three preconditions must all be true:

1. The TIA Portal instance is reachable through Openness. The TIA Openness API requires that no other TIA process owns the project exclusively, OR that the project is actively held open in the same Windows user session so the openness handshake can succeed.
2. The TIA project compiles without errors. SIMIT reads the compiled S7 blocks via Openness; unresolved references, type mismatches, or missing library references abort the read.
3. The required TIA optional packages are installed. The minimum set is the TIA Openness package plus any support package that matches the device families in the project (e.g. S7-1500, S7-1200, PLCSIM, HMI panels).

When any single condition fails, SIMIT displays the composite message rather than a per-cause error. The diagnostic flow below isolates which condition applies to a specific installation.

Diagnostic Flow

Cause 1 - TIA Portal Holds the Project Exclusively

SIMIT talks to TIA Portal through the Openness API. If TIA Portal is open and the project is loaded in the project tree on the same Windows user session, Openness can negotiate access. If TIA Portal is open on a different Windows user session, or if a previous TIA Portal process crashed without releasing the project lock file (*.lock in ...\[ProjectName]\System\), the Openness handshake fails and SIMIT reports the project as "possibly opened in a TIA instance." Confirm this branch with:

Any orphaned .lock file from a killed TIA process causes the same symptom. Delete the lock file only after verifying that no TIA Portal instance is running.

Cause 2 - TIA Project Contains Compilation Errors

The Openness API only exposes compiled blocks. If the project tree shows red icons, SIMIT aborts the import. Open the project in TIA Portal, run Compile > Software (rebuild all), and resolve every entry in the Inspector > Info > Compile tab before re-attempting the SIMIT import. Common error classes that block Openness even when the PLC is otherwise usable:

• Missing PLC hardware (device proxy not installed)
• Unresolved library master copies after a TIA upgrade
• Type conflicts between global DBs and instance DBs
• HMI tags pointing to deleted PLC tags

Cause 3 - Missing TIA Addon Packages

The SIMIT installer registers its TIA addin under Siemens\Automation\Portal Vxx\AddIns, but several required support packages are not part of the SIMIT media and must be installed separately. The minimum set for SIMIT V10 and V11 is:

Step-by-Step Resolution

1. Confirm both programs are from the same Windows user session. Run TIA Portal and SIMIT from the same login. Openness uses DCOM and does not cross session boundaries on Windows by default.
2. Open the TIA Portal project first. Launch TIA Portal V16, open the project, and let the project tree finish loading. Do not close TIA Portal during the SIMIT import.
3. Compile the project cleanly. Right-click the PLC station > Compile > Software (rebuild all). The status bar must show Compilation finished without errors.
4. Verify TIA Openness is installed. In TIA Portal: Help > Installed software. Confirm a line beginning with SIMATIC TIA Portal Openness exists for the matching V-version.
5. Verify the SIMIT TIA Coupler addin is registered. Check the folder %ProgramFiles%\Siemens\Automation\Portal V16\AddIns\SIMIT. The DLL SIMIT.TIA.AddIn.dll must be present.
6. Install the matching TIA Openness package. If the line is missing, insert the TIA Portal DVD, run the setup, and select SIMATIC TIA Portal Openness. Restart the PC after installation.
7. Install any required support packages. In TIA Portal: Options > Support packages > Install support packages. Add the latest HSP for every PLC family referenced in the project.
8. Launch SIMIT and import the project. In SIMIT, drag the TIA Portal Coupler from the catalog to the project tree, or use the menu Project > Import TIA Portal project. TIA Portal will display an Openness access prompt; click Allow within the default 30-second timeout.
9. Re-attempt the import. The error dialog should not appear. SIMIT lists the imported tags and blocks in the coupling editor.

Version Compatibility Matrix

Openness is version-locked. SIMIT and TIA Portal must be on a Siemens-released combination, or the Openness handshake fails silently and surfaces as the same error dialog. The combinations validated in the field are:

The DEMO mode of SIMIT V10.2 enforces the same coupling path as the full license, so the error appears in DEMO mode whenever any of the three causes are present.

Verification Procedure

After applying the resolution, verify that the import path is healthy using these checks:

1. Openness prompt is shown only once per session. The first import of a project causes TIA Portal to display the access prompt. Subsequent imports in the same session do not.
2. SIMIT coupling editor lists tags. In SIMIT, double-click the imported TIA coupler. The Signals tab must show every PLC tag referenced by the project. Empty lists indicate that the import still failed silently.
3. PLCSIM instance starts. If you used the PLCSIM coupler, the PLCSIM instance must start and the connection state in the SIMIT status bar must show Connected in green within 10 seconds.
4. Round-trip a tag. Force a Boolean tag in the TIA project, recompile, and read it through a SIMIT signal. A value change within 200 ms confirms the Openness tag subscription is live.
5. Restart the PC. Restart Windows and re-run the import cold. If the error returns, an Openness DCOM permission is missing on the Windows user account.

DCOM and Windows Account Hardening

TIA Openness uses DCOM and WMI to communicate with TIA Portal. On hardened Windows installations, the Openness call returns E_ACCESSDENIED and SIMIT displays the same error message. Configure the following on the Windows account that runs SIMIT and TIA Portal:

• Member of the local group DCOM Users or Distributed COM Users.
• Launch and Activation Permissions for the TIA Portal COM application (run dcomcnfg, navigate to Component Services > Computers > My Computer > DCOM Config > Siemens TIA Portal, and grant the account Local Launch and Local Activation rights).
• Access Permissions must include the account with Allow for Local Access and Remote Access.
• Windows Firewall rule allowing inbound TCP 135 (DCOM endpoint mapper) and the dynamic range 49152-65535 for the local subnet.

After applying DCOM changes, restart the COM+ Event System and the DCOM Server Process Launcher services, then re-run the import.

Cleanup of Orphan Locks

When TIA Portal crashes, the project lock file *.lock is left in the project folder. The next Openness call returns project already in use. To clean the lock safely:

tasklist | findstr "Portal.exe"
taskkill /f /im Portal.exe
del /s /q "%USERPROFILE%\Documents\Automation\<Project>\*.lock"

Only run the del command after confirming that no TIA Portal process is active. The lock file is recreated automatically by TIA Portal the next time the project is opened.

Field-Proven Workarounds

Preventive Configuration

• Always run SIMIT and TIA Portal as the same Windows user, in the same session.
• Keep the SIMIT version and the TIA Portal version on a Siemens-released compatibility pair. Mixing SIMIT V10 with TIA V17, for example, breaks Openness even though both products install cleanly.
• Apply Siemens hotfixes to both products on the same maintenance window. Hotfix KB entries that touch Openness are referenced in the SIMIT release notes.
• Disable Windows fast startup when commissioning, as fast startup has been observed to leave stale DCOM bindings that break the Openness handshake on the first cold boot.

FAQ