How to Resolve WinCC Client 'SFC Init Error' in SIMATIC PCS 7 Sequential Function Charts

In SIMATIC PCS 7 V7.1 SP3, the runtime popup 'SFC Init Error' appearing on WinCC Operator Station (OS) Clients when opening an SFC faceplate or embedded ActiveX control occurs when the client's local server data package (*.pck) is desynchronized from the active OS Server or when an SFC chart was modified or deleted on the Engineering Station without completing a full OS compile and package download. While restarting WinCC on the client temporarily clears the error by flushing stale memory handles, permanent resolution requires executing an OS compilation with server package generation, downloading the updated server package to all OS Clients, and verifying SFC Visualization license availability.

Architecture of SFC Client-Server Visualization and Package Files

In distributed SIMATIC PCS 7 architectures, OS Clients do not communicate directly with S7-400 controllers for SFC visualization:
* The Visualization Pipeline:
* The SFC execution engine resides in the controller (OB32–OB38 cyclic tasks).
* The OS Server runs the SFC Server Service (sfc_rt.exe), polling controller SFC system data blocks (SDBs) and instance data blocks.
* The OS Client renders the sequential flow using the PCS 7 SFC Control ActiveX component (@pg_@sfc_rts.pdl).
* The Role of Server Data Packages (*.pck):
* To display an SFC, the OS Client queries the local server data package generated during OS compilation.
* The package file contains symbolic routing pointers linking the SFC chart name to the owning OS Server.
* If an SFC chart is renamed, moved to another plant hierarchy folder, or deleted, the client's local cache retains stale pointers, causing initialization failure: SFC Init Error.

Root Causes of 'SFC Init Error' on WinCC Clients

Forensic investigation identifies three distinct triggers:
1. Asymmetric Engineering Downloads: An engineer compiled and downloaded CFC/SFC changes to the automation station, but omitted compiling the OS or downloading updated server data packages to the OS Clients.
2. Orphaned SFC Control Object: A graphic picture contains an embedded PCS 7 SFC Control whose SFCName property points to a legacy SFC chart that no longer exists in the project.
3. WinCC Client Memory Cache Desynchronization: After an OS Server failover or network glitch, the client's background DCOM connection to sfc_rt.exe becomes invalid. Toggling the client offline/online resets DCOM handles, temporarily masking the underlying package mismatch.

Server Data Package Generation and Client Download Workflow

To permanently resolve the error across all operator clients:

Compile OS on the Engineering Station:
* In SIMATIC Manager, right-click the OS Server object: select Compile.
* Scope: Select Changes Only (or Entire OS if structural hierarchy changes were made).
* Confirm that the option Generate Server Data is checked.
Update Server Data on OS Clients:
* In SIMATIC Manager, right-click each OS Client project: select Server Data....
* Select the imported OS Server package: click Update.
Download to OS Server and Clients:
* Download changes to the OS Server: PLC > Download > Changes.
* Download the updated client projects to all physical OS Clients.

Re-Linking Corrupted SFC ActiveX Controls in Graphics Designer

If the error occurs on a specific picture screen rather than globally:

Open the offending picture in Graphics Designer on the ES.
Select the embedded PCS 7 SFC Control object.
Open the Properties dialog: inspect parameter SFCName.
Verify that the configured string matches the current plant hierarchy path identically (e.g., Plant1/Reactor1/SFC_Phase1).
If invalid, click the browse button, select the active SFC chart from the project tree, and save the picture.
Re-download the modified picture file to the OS Server and Clients.

Comparison of SFC Runtime Error Signatures and Remedies

The table below outlines common SFC Visualization errors encountered on WinCC operator stations.

Error MessageFailure LocationPrimary Root CauseCorrective Action'SFC Init Error'OS ClientStale server data package / Deleted SFCUpdate server data package & download'SFC not found on server'OS Server / ClientAS-OS tag compilation omittedCompile OS and generate server data'No authorization for SFC'OS Client FaceplateUser lacks Level 5/6 process rightsAssign user rights in User Administrator'Communication error to AS'OS ServerS7 connection between AS and OS lostCheck Plant Bus cables & NetPro'ActiveX component missing'OS ClientMissing PCS 7 SFC Visualization setupRun PCS 7 Client software installer

Verification

To confirm that the SFC Init Error is resolved:
1. On the OS Client, launch WinCC Runtime.
2. Navigate to the picture containing the SFC or click the SFC block icon.
3. Confirm that the SFC visualization window opens cleanly within 1 second without displaying SFC Init Error.
4. Verify that the SFC chart layout, step names, and transition conditions render completely with active step timing displayed.
5. In the WinCC Diagnose folder on the client, open WinCC_Sys_01.log: confirm zero DCOM or SFC initialization error records.

Limitations and Operational Precautions

Never delete or rename active production SFC charts while an automated batch sequence is running in the controller; abort or complete the batch prior to engineering changes.
Ensure all OS Clients have identical versions of SFC Visualization installed; mixing client software service packs will cause ActiveX initialization faults.
Do not attempt manual file copies of .pck files in Windows Explorer; always use SIMATIC Manager's automated server data update mechanism.
Always validate final software licensing, SFC visualization packages, and system documentation against the applicable Siemens catalog and authorized distributor quotation.

Engineer FAQ

Why did restarting WinCC on the client temporarily fix the error?

Restarting WinCC killed the cached client process handles and forced the client to re-read the server data package from disk upon startup, temporarily clearing stale memory pointers.

Can I view SFCs on an OS Web Client?

Yes, provided the WinCC Web Navigator client has the PCS 7 SFC Visualization Web plugin installed and the server data package is published.

What license is required on the client for SFC visualization?

In standard PCS 7 architectures, OS Clients do not require separate SFC runtime licenses; the SFC Visualization license is installed centrally on the OS Server.