Resolving 'api-ms-win-crt-runtime-l1-1-0.dll Missing' During PCS 7 Station Configuration

During the installation or startup of the SIMATIC Station Configuration Editor in PCS 7 V9.0 SP1, the system error 'The program can't start because api-ms-win-crt-runtime-l1-1-0.dll is missing from your computer' indicates that the operating system is missing the Microsoft Visual C++ Universal CRT (Universal C Runtime) component. Additionally, PCS 7 V9.0 SP1 is officially certified for Windows Server 2016 and Windows 10 Enterprise LTSB, and is unsupported on Windows Server 2012. To resolve this error, deploy the official operating system (Windows Server 2016), or on existing installations, install Microsoft cumulative prerequisite updates KB2919355 and KB2999226 followed by the Microsoft Visual C++ 2015 Redistributable package.

Universal C Runtime (UCRT) Architecture in Industrial Automation

Modern industrial automation applications—including SIMATIC NET, Station Configuration Editor (s7opcadx.exe), and WinCC V7.4—are compiled using modern Microsoft Visual Studio compilers. These 32-bit and 64-bit binaries rely on the Universal C Runtime (UCRT), an operating system component introduced by Microsoft to standardize core C/C++ library routines across Windows platforms.

The core dynamic link library for the Universal CRT is api-ms-win-crt-runtime-l1-1-0.dll (along with related api-ms-win-crt-*.dll modules). In modern Windows releases (Windows 10 and Windows Server 2016), the Universal CRT is embedded natively into the operating system kernel. However, on older or unpatched Windows platforms (such as Windows Server 2012 R2 or Windows 7), UCRT is not native and must be installed via Microsoft Windows Update KB2999226.

Root Causes of Missing Runtime DLL Errors in PCS 7

When an engineer installs PCS 7 V9.0 SP1 and encounters the runtime DLL failure upon launching Station Configuration Editor, technical analysis reveals three root failure modes:

Deploying on an Unsupported Operating System (Windows Server 2012): PCS 7 V9.0 SP1 is not certified or released for Windows Server 2012. Siemens officially supports PCS 7 V9.0 SP1 exclusively on Windows Server 2016 Standard Edition (64-bit) and Windows 10 Enterprise 2015 LTSB (64-bit). Installing on unapproved server editions leaves critical system dependencies unfulfilled.
Missing Windows Update KB2999226 (Universal CRT): If installed on an unpatched Windows server, the operating system lacks the Universal C Runtime updates. When s7opcadx.exe attempts to initialize the PC Station communication stack, Windows aborts execution with the missing DLL dialog.
Incomplete or Damaged Visual C++ 2015 Redistributable: The Siemens installer deploys the Microsoft Visual C++ 2015 Redistributable silently. If a previous third-party application locked runtime files during setup, the redistributable fails silently, omitting the runtime registration in C:\Windows\System32\.

Operating System Updates and Visual C++ Dependency Matrix

The following table details the Microsoft updates and Visual C++ prerequisites required for PCS 7 communication tools:

Component / UpdateMicrosoft KB ReferenceTarget Windows VersionRole in Resolving DLL FaultWindows Server 2016Native OS BuildCertified for PCS 7 V9.0 SP1Recommended; includes native UCRTWindows Update RollupKB2919355Windows Server 2012 R2Mandatory prerequisite for all subsequent KBsUniversal C RuntimeKB2999226Server 2012 / Windows 7Directly delivers api-ms-win-crt-runtime-l1-1-0.dllVisual C++ 2015 Redistvc_redist.x86 / x64All Windows platformsRegisters C++ runtime libraries and COM bindingsSIMATIC Security ControlSiemens Security ToolPCS 7 Installation MediaSets DCOM permissions for PC Station daemon

Step-by-Step Procedure to Install Universal CRT and Visual C++

To resolve the missing DLL error and establish functional Station Configuration Editor communication:

Align with Supported Operating System Baseline (Recommended):
- For production stability, deploy Windows Server 2016 Standard Edition (64-bit) using official installation media.
- Complete all pending Windows cumulative updates prior to running PCS 7 setup.
Manual Remediation on Existing Server Installations:
- If operating in a test environment on Windows Server 2012 R2, verify whether update KB2919355 (Windows Server 2012 R2 Update) is installed via Control Panel -> Programs and Features -> View installed updates.
- If absent, download and install KB2919355 from the Microsoft Download Center; reboot the server.
Install Universal C Runtime (KB2999226):
- Download KB2999226 (Update for Universal C Runtime in Windows) for Windows Server 2012 R2 (64-bit).
- Run the standalone update installer (Windows8.1-KB2999226-x64.msu).
- Complete the installation and reboot.
Reinstall Microsoft Visual C++ 2015 Redistributable:
- Browse to the PCS 7 installation media directory: ...\04_Prerequisites\VCRedist\ (or download from Microsoft).
- Run vc_redist.x64.exe as Administrator; select Repair (or Install).
- Run vc_redist.x86.exe as Administrator; select Repair (or Install).
- Both 32-bit and 64-bit redistributables must be installed, as SIMATIC NET operates hybrid processes.
Restart and Launch Station Configuration Editor:
- Restart the server.
- Click the Station Configuration Editor icon in the Windows notification tray (or launch s7opcadx.exe).
- Confirm that the utility launches cleanly, displaying active virtual PC station slots.

Verification

Verify Station Configuration Editor and PC Station readiness:
1. Confirm that Station Configuration Editor opens without throwing DLL or COM exceptions.
2. In Station Configuration Editor, verify that slot 1 (WinCC Application) and network communication processors (IE General) display status RUN (green checkmark).
3. In SIMATIC Manager, select the PC Station and execute PLC -> Download; verify that the hardware configuration downloads cleanly over the local loopback.
4. Launch WinCC Explorer; verify that the project connects to the local computer without communication manager errors.

Limitations and Operational Precautions

Unsupported Production Warning: Operating PCS 7 V9.0 SP1 on Windows Server 2012 is strictly rejected by Siemens Customer Support; production systems must utilize Windows Server 2016.
Clean Media Sourcing: Always source Windows operating system installation media from official Microsoft Volume Licensing channels; modified ISOs downloaded from third-party sites frequently strip out core servicing stacks.
Windows Firewall Exceptions: Ensure SIMATIC Security Control is executed after installing Visual C++ runtimes to re-verify firewall rules.

Engineer FAQ

What causes the api-ms-win-crt-runtime-l1-1-0.dll missing error?

The error occurs when the Windows operating system lacks the Universal C Runtime (UCRT) component or the Microsoft Visual C++ 2015 Redistributable.

Is PCS 7 V9.0 SP1 supported on Windows Server 2012?

No. PCS 7 V9.0 SP1 is officially supported exclusively on Windows Server 2016 Standard Edition (64-bit) and Windows 10 Enterprise 2015 LTSB.

Which Microsoft KB update provides the missing DLL?

Microsoft update KB2999226 (Update for Universal C Runtime) delivers api-ms-win-crt-runtime-l1-1-0.dll.

Why must both 32-bit and 64-bit Visual C++ redistributables be installed?

SIMATIC PCS 7 runs a hybrid architecture: the operating system is 64-bit, but many engineering tools (STEP 7, CFC) and communication daemons run in 32-bit compatibility mode.