Resolving PCS7 V6 Error 1305: S7pplomx.dll Read Failure

Problem Overview

When launching the PCS 7 V6 setup on a workstation that already has STEP 7 V5.2 SP1 installed, the Windows Installer (MSI) engine halts with the following dialog:

Error 1305: Error reading from file C:/SIEMENS/STEP7/S7BIN/S7pplomx.dll. Verify that the file exists and that you can access it.

After this dialog is acknowledged, the PCS 7 V6 installation rolls back. In most cases the existing STEP 7 V5.2 SP1 installation is also flagged as inconsistent, so subsequent re-runs of either setup fail with the same message until the underlying file-state problem is corrected.

Error 1305 is a generic Microsoft Windows Installer return code. It is raised by the MSI runtime (msiexec.exe) when a file that is referenced in the File table of an .msi/.msp package cannot be opened, read, hashed, or copied during the InstallFiles, PatchFiles, or Advertise cost phase. The error is not specific to Siemens software; it can be triggered by any installer that references a cabinet file or a dependent DLL.

Affected Products and Versions

Root Cause Analysis

The S7pplomx.dll file is shipped by the STEP 7 V5.2 SP1 package. PCS 7 V6 setup detects the existing STEP 7 installation, enumerates its files, and re-validates the cabinet signature for S7pplomx.dll as part of its prerequisite check. Error 1305 is raised when one of the following is true:

1. The S7pplomx.dll file is missing from C:\SIEMENS\STEP7\S7BIN. This typically happens after an aborted STEP 7 uninstall, an antivirus quarantine, or a disk-imaging restore that excluded the S7BIN folder.
2. The file is present but locked by another process. Common offenders are S7WBEXEF.exe, the SIMATIC Manager, a stray dllhost.exe holding a COM surrogate, or antivirus on-access scanners.
3. The file is present but truncated or corrupted, e.g. by an incomplete disk write, a failing sector, or a CD/DVD read error during the original install.
4. The MSI package cannot access the file because of an NTFS access-denied condition. The SYSTEM account or the user running the install does not have Read & Execute on the file.
5. The dependent Microsoft Visual C++ / MFC runtime that S7pplomx.dll links against is not registered, so the loader cannot read the PE header cleanly and MSI treats the file as unreadable.

Siemens documents the same symptom and the manual file-copy remediation in the support FAQ entry Entry ID 20383534 on the Siemens Industry Online Support portal, specifically in the procedure step labeled P4. The reference is the canonical starting point for this failure mode on PCS 7 V6 / STEP 7 V5.2 SP1.

Pre-Checks Before Remediation

Capture the current state before changing anything, so a rollback is possible:

1. Open Control Panel → Add or Remove Programs (Windows XP) or Programs and Features (Windows Server 2003) and record the exact STEP 7 version string. It must read SIMATIC STEP 7 V5.2 + SP1 or higher SP-level; if the SP1 suffix is missing, the patch was not installed and that is a separate problem.
2. Open an elevated command prompt and run:
   dir /a "C:\SIEMENS\STEP7\S7BIN\S7pplomx.dll"
   Note the file size, the date, and whether the file is reported as present.
3. Run sfc /scannow from the elevated prompt. This is the Windows File Protection check and will flag any protected system DLL that has been overwritten.
4. Open Event Viewer → Application and clear the log. Re-run the PCS 7 V6 setup once and capture the new MSI event. The MSI event log entry under source MsiInstaller with Event ID 10005 typically echoes the file path that MSI failed to read.
5. Verify free disk space on C:. PCS 7 V6 needs roughly 1.5 GB of free space during the install plus the same again as a rollback staging area on the system drive.

Remediation Procedure

Step 1 - Stop All SIMATIC Processes

1. Press Ctrl+Shift+Esc and terminate the following executables if present:
   S7WBEXEF.exe, SIMATIC_Manager.exe, S7HCOM_X.exe, S7httrace.exe, ccstart.exe, S7epa.exe.
2. Stop the SIMATIC diagnostic services:
   net stop s7diagbx && net stop s7events && net stop s7oiehsx
3. Disable the antivirus real-time scan on C:\SIEMENS\ for the duration of the install. Symantec Endpoint Protection and McAfee are known to hold short-lived read handles on DLLs that MSI then cannot acquire.

Step 2 - Re-stage S7pplomx.dll Manually

This is the procedure corresponding to step P4 in Siemens FAQ 20383534. It does not require booting into safe mode, but it does require local administrator rights.

1. Insert or mount the STEP 7 V5.2 SP1 installation medium.
2. Browse the medium. The DLL is located in the cabinet layer of the STEP 7 setup. On a typical V5.2 SP1 CD image the path is:
   D:\Setup\STEP7\Disk1\S7pplomx.dl_
   Note the trailing underscore - this is the cabinet-compressed form. The expanded form is S7pplomx.dll.
3. Use expand.exe (a Windows native tool, present on every supported OS) to decompress the cabinet entry into the S7BIN folder:
   expand "D:\Setup\STEP7\Disk1\S7pplomx.dl_" "C:\SIEMENS\STEP7\S7BIN\S7pplomx.dll"
4. If the cabinet is not exposed on the medium (some Service Pack slipstream images hide it), an alternative is to copy the file from a known-good peer installation of STEP 7 V5.2 SP1 with the same language pack, then run regsvr32 /s "C:\SIEMENS\STEP7\S7BIN\S7pplomx.dll" from the elevated prompt to re-register it.
5. After the file is in place, set the NTFS rights to match the existing siblings in the folder:
   cacls "C:\SIEMENS\STEP7\S7BIN\S7pplomx.dll" /E /G "Authenticated Users":R
cacls "C:\SIEMENS\STEP7\S7BIN\S7pplomx.dll" /E /G "Users":R
6. Verify:
   dir /a "C:\SIEMENS\STEP7\S7BIN\S7pplomx.dll"
   Confirm the size is in the expected range (typically 245 KB to 280 KB depending on language) and the date matches the STEP 7 V5.2 SP1 release date.

Step 3 - Repair the STEP 7 V5.2 SP1 Installer State

Even with the file on disk, the MSI database for STEP 7 may still be marked inconsistent. Repair it before re-launching the PCS 7 setup:

1. Open Control Panel → Add or Remove Programs, select SIMATIC STEP 7 V5.2, and click Change → Repair.
2. If the repair option is not present, run the STEP 7 setup with the maintenance switch:
   "D:\Setup\STEP7\setup.exe" /repair
3. Reboot when the repair completes. A reboot is required to release any cached file handles held by the explorer shell extension that STEP 7 registers at logon.

Step 4 - Re-launch the PCS 7 V6 Setup

1. Log in as a local administrator (not as a domain user with delegated rights - the PCS 7 setup creates local services and DCOM entries that domain policies can block).
2. Disable UAC if it is present (it is not the default on Windows XP SP2, but some hardening images turn it on).
3. Mount the PCS 7 V6 DVD. Run setup.exe as administrator.
4. On the Installation Type dialog select Complete for a single-station engineering install, or Custom for an ES/OS split install.
5. Watch the InstallFiles phase. If the installer re-displays Error 1305, the cabinet on the DVD is itself corrupted. Re-image the DVD from a known-good ISO.

Step 5 - Post-Install Verification

1. Confirm the PCS 7 V6 entry appears in Programs and Features with the expected build number.
2. Confirm the SIMATIC Manager opens and that the Options → PCS 7 menu is present (this proves the V6 overlay installed on top of V5.2 SP1).
3. Run the PCS 7 Self-Diagnosis tool from Start → SIMATIC → PCS 7 → Self-Diagnosis. It should report a green status for all components including the OMX interface that S7pplomx.dll implements.
4. Start WinCC Explorer and confirm a new project can be created without OMX errors in the diagnostic trace.

Error Code Reference

The full enumeration of MSI return codes is published by Microsoft in the Windows Installer error message reference. Use the code, not the dialog text, when searching the Siemens support database - the same dialog text can map to multiple root causes depending on the file the MSI engine is operating on.

Alternative Recovery Paths

If the manual copy described in Step 2 does not clear the failure, work the list top to bottom:

1. Re-apply the STEP 7 V5.2 SP1 patch in maintenance mode. This rewrites all cabinet files and re-registers all COM objects.
2. Recreate the S7BIN folder by uninstalling STEP 7 V5.2 SP1, manually deleting the residual C:\SIEMENS tree, reinstalling STEP 7 V5.2 base, and then re-applying SP1. This is the cleanest path and is mandatory if SFC has flagged any protected DLLs as inconsistent.
3. Use the Windows Installer CleanUp utility (msicuu.exe) only as a last resort. It removes the MSI database entries for STEP 7 and forces a full reinstall but it does not remove the file residue, so it must be combined with the manual folder deletion above.
4. Check the registry at HKLM\SOFTWARE\Siemens\AUTSW\STEP7. The Path value must point at the same C:\SIEMENS\STEP7 folder where S7pplomx.dll was placed. A path mismatch (e.g. D:\SIEMENS\STEP7 after a drive letter change) is a frequent silent cause of the same error on re-install.

Troubleshooting Matrix

Related Considerations

STEP 7 V5.2 SP1 is the last release that supports Windows 2000. If the engineering station is being prepared for a later PCS 7 release (V7, V8, V9), the correct long-term path is to upgrade the base STEP 7 to V5.5 SPx first and then install the matching PCS 7 DVD, rather than trying to install PCS 7 V6 over a V5.2 base. The Error 1305 failure mode is much rarer on V5.5-era media because the cabinet layout and the S7BIN file count are simpler.

For batch deployments across multiple engineering stations, capture the S7pplomx.dll from one good host and roll it out via a startup script. The file is bit-identical for a given language and SP level, so a script-driven copy plus a regsvr32 /s call can pre-empt the error before the PCS 7 setup ever runs.

Field-Commissioning Checklist

1. Verify OS is Windows XP SP2 or Windows Server 2003, fully patched.
2. Verify local administrator logon.
3. Verify C:\SIEMENS\STEP7\S7BIN\S7pplomx.dll exists, has expected size, and is not locked.
4. Verify HKLM\SOFTWARE\Siemens\AUTSW\STEP7\Path points at the right drive.
5. Verify free disk space >= 3 GB on system drive.
6. Stop all SIMATIC processes and AV real-time scan.
7. Repair STEP 7 V5.2 SP1 in maintenance mode.
8. Reboot.
9. Run PCS 7 V6 setup as administrator.
10. Run PCS 7 Self-Diagnosis and confirm green status.