Resolving S7-PLCSIM Startup Errors in PCS 7 V4.02 Conversion Projects

Engineers maintaining or migrating legacy SIMATIC PCS 7 V4.02 projects routinely hit a hard wall the first time they try to open the integrated S7-PLCSIM simulator from the STEP 7 / CFC editor. The error appears even when the PLCSIM authorization appears intact, the PLCSIM package has been reinstalled, and the entire Engineering Setup (ES) has been rebuilt from scratch. This reference explains the underlying causes, isolates the most common failure modes, and provides a field-proven recovery procedure that lets you bring the simulated AS (Automation Station) online so the project can be carried through the V4 → V5.2 → V6.1 → V7.1 → V8.0 conversion chain.

1. Problem Scope and Symptom Description

The reported failure mode is reproducible on a clean engineering station:

• PCS 7 V4.02 engineering setup installed on Windows 2000 / Windows XP (32-bit).
• S7-PLCSIM V5.1 or V5.2 installed as a child package of STEP 7 V5.1.
• Valid S7-PLCSIM license key on hard disk, recognized by AuthorsW.exe in Control Panel.
• User clicks Options > Simulate Modules (German: Optionen > Baugruppen simulieren) or invokes the simulation button from the S7 program / CFC / SFC editor.

Typical dialog text observed:

• "S7-PLCSIM could not be started."
• "The PLCSIM component is not installed. Please install S7-PLCSIM."
• "Internal error: PLCSIM interface not available (error code 0x000A)" or similar hex codes returned by S7otbxdx.dll.
• Silent failure — the SIM table opens, but the simulated CPU does not reach RUN and remains in STOP with diagnostic buffer entry "OB not loaded / Communication error to PLCSIM".

Because PCS 7 V4.02 predates the integrated TIA Portal environment, the simulator is loaded by the S7-PLCSIM service rather than the TIA Portal runtime. The error path therefore runs through the STEP 7 V5.1 component layer, not the TIA Portal layer used by modern S7-PLCSIM Advanced documentation.

2. Affected Software Stack and Compatibility Matrix

3. Root Cause Analysis

Five independent root causes have been observed in the field. Diagnose in the order listed because each is faster to verify than the next.

3.1 Component layer mismatch (most common)

The SIMATIC Manager launches PLCSIM through the S7winsfx.exe stub linked against s7otbxdx.dll v5.1.3.x. If a newer STEP 7 (V5.3 or higher) has been installed on the same image — even temporarily, even partially — the COM class registration under HKEY_CLASSES_ROOT\S7-PLCSIM.Application is overwritten with the newer build's GUID. STEP 7 V5.1 cannot re-register against the newer interface, and the dialog "PLCSIM component is not installed" appears even though the binary is on disk.

3.2 Authorization database corruption

PCS 7 V4.02 uses the legacy WIBU-KEY / AuthorsW license path. The wibukey.sys kernel driver and the AXDB*.DLL pair must be version-matched. A blue-screen crash, an interrupted uninstall, or a disk-image restore can leave the AXDB_Database file in %ProgramFiles%\Siemens\Automation\ inconsistent with the wibukey.sys driver. The license is then visible in Control Panel but cannot be checked out to the PLCSIM process.

3.3 Service pack drift

PCS 7 V4.02 SP3 + HF7 plus STEP 7 V5.1 SP6 are the minimum service levels. Skipping any intermediate hotfix introduces a known mismatch in the PLCSIM interface table; the symptom is OB100 load failure on the simulated CPU.

3.4 Windows OS upgrade or DEP/NX state

Windows XP SP3, Windows Vista, and Windows 7 (32-bit) enable DEP/NX for all processes by default. PCS 7 V4.02 binaries (built 2001) contain non-NX-compatible code sequences and may refuse to start the PLCSIM host. The same applies to the Windows Installer 4.5 upgrade that ships with XP SP3.

3.5 Project-side fault: incorrect target CPU or missing blocks

If the project was opened in a newer PCS 7 version and saved, the S7-PROG\<CPU>\S7 container may contain references to OB121 / OB122 / SFB / SFC blocks that the V5.1 runtime cannot resolve. The simulated CPU enters STOP, and the user concludes that "PLCSIM is broken" when in fact the project is broken.

4. Pre-Flight Diagnostic Procedure

Run the following checks before any reinstall to gather evidence that isolates the root cause.

1. Verify the license key. Open Control Panel → SIMATIC Manager → License Management (or run AuthorsW.exe from %ProgramFiles%\Siemens\Automation\). Confirm the S7-PLCSIM license is listed with status OK, the host ID matches the current machine, and the transferred-to-disk checkbox is set if you are using a soft container.
2. Verify the COM class registration. From an elevated command prompt: reg query HKEY_CLASSES_ROOT\S7-PLCSIM.Application /s. The InprocServer32 default value must point to S7otbxdx.dll under the original V5.1 install path. If the path contains a V5.3/V5.4 folder, root cause 3.1 is confirmed.
3. Verify PLCSIM binary version. Right-click S7-PLCSIM.exe in SIEMENS\Automation\S7-PLCSIM\Bin\, select Properties → Version. The file version must report 5.1.x.x (e.g. 5.1.3.0 for SP3). A 5.2.x.x or 5.3.x.x file on a STEP 7 V5.1 host will not be recognized.
4. Check the diagnostic buffer of the simulated CPU. After the failure, open the SIM table and read the diagnostic buffer entries. An "OB not loaded" entry on OB100, OB121, or OB122 points to root cause 3.5 (project-side).
5. Check event log. Windows Event Viewer → Application log. Look for S7-PLCSIM and S7otbxdx sources. Event ID 7000/7011 service-start failures indicate authorization problems (root cause 3.2).
6. Check DEP status. Run wmic OS Get DataExecutionPrevention_SupportPolicy. A return value of 2 (OptOut) or 3 (AlwaysOn) requires a per-binary exception (see §5.4).

5. Step-by-Step Recovery Procedure

Apply the steps in order. Each step is independently verifiable.

5.1 Restore the component layer (root cause 3.1)

1. Uninstall any STEP 7 version newer than V5.1 from Control Panel → Add/Remove Programs in the strict order: SIMATIC PCS 7 ES, then S7-PLCSIM, then STEP 7, then Automation License Manager.
2. Manually delete the residual folder %ProgramFiles%\Siemens\Automation\S7\* if it points to a V5.3/V5.4 build.
3. Reinstall the original PCS 7 V4.02 DVD image, choosing Modify and re-enabling the S7-PLCSIM component.
4. Re-register the PLCSIM COM object: regsvr32 "%ProgramFiles%\Siemens\Automation\S7-PLCSIM\Bin\S7otbxdx.dll" from an elevated command prompt. The dialog must confirm DllRegisterServer succeeded.
5. Restart the engineering station.

5.2 Repair the authorization database (root cause 3.2)

1. Stop the WIBUKEY service: net stop "WIBU-KEY server".
2. Back up and delete %ProgramFiles%\Siemens\Automation\AXDB*.*.
3. Run AuthorsW.exe /repair (or use the Repair License Database action in the License Management dialog).
4. Re-transfer the PLCSIM license from the source license container (floppy disk, USB dongle, or .zip soft container).
5. Restart the WIBUKEY service and verify the license shows OK in License Management.

5.3 Apply the full service-pack stack (root cause 3.3)

1. Install STEP 7 V5.1 SP6 first.
2. Install S7-PLCSIM V5.1 SP3 (or the latest available hotfix shipped with PCS 7 V4.02 HF7).
3. Install the PCS 7 V4.02 SP3 → HF7 stack, restarting the workstation only when prompted.
4. Re-verify the file versions listed in §4 step 3.

5.4 Configure DEP/NX exclusion (root cause 3.4)

1. Open System Properties → Advanced → Performance → Settings → Data Execution Prevention.
2. Select Turn on DEP for essential Windows programs and services only (the OptOut mode, value 2).
3. If the policy is forced to AlwaysOn (value 3) by group policy, the workstation must be re-imaged with a pre-SP3 XP image, or moved to a virtual machine running Windows 2000 SP4 / XP SP2 32-bit.

5.5 Sanitize the project before opening the simulator (root cause 3.5)

1. Open the project in SIMATIC Manager, right-click the S7 Program, and select Check Block Consistency.
2. Compile all blocks: Program → Compile All. Resolve any SF / FC / DB / UDT version-mismatch warnings.
3. Confirm the target CPU type (e.g. AS 416, AS 417) matches the PLCSIM-supported type list. PCS 7 V4.02 supports CPU 416-2 DP and CPU 417-4 in PLCSIM V5.1; H-CPUs require PLCSIM V5.3 or later and will not load on V4.02.
4. Download the cleaned program to the simulated CPU: PLC → Download with the SIM path active.

6. Verification Checklist

After applying the recovery procedure, the simulation path is healthy when all of the following are true:

• SIMATIC Manager opens without re-asking for the PLCSIM license.
• The Simulate Modules command launches S7-PLCSIM.exe with a visible window and a CPU in STOP-RUN-Switch → RUN.
• A test OB1 with a single "SET / = Q0.0" downloads successfully and toggles output Q0.0 in the SIM table monitor.
• CFC charts of the AS open in read-only view; the chart-in / chart-out signals are visible in the SIM table.
• The diagnostic buffer shows No fault on every restart.

7. The V4 → V8 Conversion Path

Once PLCSIM is functional, the project is ready for staged migration. Each step must be performed in sequence; skipping a version produces unsupported tag types and import errors.

8. Modern Alternative: S7-PLCSIM Advanced

For new development, Siemens recommends S7-PLCSIM Advanced, which runs on TIA Portal V17 or later on a 64-bit Windows 10/11 host. PLCSIM Advanced supports the safety program testing workflow documented at the Siemens documentation portal: Testing the safety program with S7-PLCSIM/S7-PLCSIM Advanced. While the modern API is not backward-compatible with PCS 7 V4.02, the upgrade target PCS 7 V8.x or V9.x can be developed and tested in PLCSIM Advanced once the conversion is complete, eliminating the need to keep the legacy engineering image alive indefinitely.

9. Troubleshooting Matrix

10. Field-Proven Caveats

• Never run S7-PLCSIM from a network share — the WIBU-KEY driver refuses the license check-out if the binary path is UNC.
• Disable antivirus real-time scanning on the Siemens\Automation folder during install; the WIBU-KEY installer writes to a kernel driver location that some AV products quarantine.
• If the engineering station is part of a domain, the WIBU-KEY service must be configured with a domain account that has Log on as a service privilege, otherwise the license is loaded at boot but released on first use.
• Do not enable Windows Simple File Sharing on the engineering station; it rewrites DCOM security descriptors and breaks the SIM Manager connection.