Resolving Sinamics Integrated Connection Errors on SIMOTION D435

Problem Overview

When commissioning a SIMOTION D435 (order family 6AU1435-...) with an integrated SINAMICS S120 drive controller (commonly referenced as SINAMICS Integrated), SCOUT engineering software version 4.1.5.6 can establish a connection to the SIMOTION CPU but fails to open the integrated SINAMICS drive with the dialog message "Error occurred while establishing a connection." Standard PG/PC settings are correctly configured because the SIMOTION side already communicates and accepts a project download. This symptom is not a hardware failure of the drive; it is a routing or configuration state in the engineering project that prevents the SCOUT online view from traversing from the SIMOTION CPU to its subordinate SINAMICS Integrated object.

The same condition class is reported in WinCC Unified runtime environments where an integrated connection from the HMI to a SIMATIC S7-300/400 cannot be established when the integrated connection is not configured in the PLC hardware configuration. The official Siemens documentation explicitly identifies missing hardware configuration as one cause of the same connection failure class, validating the routing/configuration interpretation for the SIMOTION D case (Causes of a faulty connection (RT Unified)).

SIMOTION D435 and SINAMICS Integrated Architecture

The SIMOTION D435 is a SIMOTION D-class motion controller with SINAMICS S120 drive control physically located on the same backplane/rack. The integrated drive is not a separate node on PROFINET; it is exposed to SCOUT as a logical sub-device under the SIMOTION CPU. Communication from SCOUT to SINAMICS Integrated therefore uses S7 routing through the SIMOTION CPU, similar to how a TIA Portal HMI uses an integrated connection to reach an S7 CPU.

Because SCOUT must traverse the SIMOTION CPU to reach SINAMICS Integrated, the project in SCOUT must contain a complete HW Config and a NetPro configuration that includes both the SIMOTION CPU as an S7 station and an S7 routing entry from the PG/PC to the integrated drive. Without this routing entry, SCOUT only resolves the SIMOTION CPU and the online view of the drive remains grey or rejects the connection.

Root Cause Matrix

Verifying the PG/PC Interface Assignment

Open SCOUT, then on the menu bar select Options > Set PG/PC Interface. Confirm the access point used for SCOUT (default: S7ONLINE (STEP7) -> TCP/IP <NIC>) is bound to the physical Ethernet adapter that is physically connected to the SIMOTION D435.

1. Open Control Panel > Set PG/PC Interface on Windows.
2. Select the access point S7ONLINE (STEP7) for the SCOUT work area.
3. Assign the correct TCP/IP adapter (avoid virtual adapters, VPN taps, and Hyper-V switches).
4. Verify the assigned NIC has link light activity when connected to the D435.
5. Return to SCOUT and use Target system > Reachable nodes (Lifelist) to confirm the SIMOTION CPU is visible.

The Lifelist (German: "Erreichbare Teilnehmer") is the standard SCOUT diagnostic for confirming the route to the controller before any project is opened. Expand the discovered SIMOTION D node; if SINAMICS Integrated appears as a child node, the routing is healthy from the network perspective.

Configuring S7 Routing in NetPro

SCOUT and STEP 7 use NetPro to define the S7 routing path from the PG/PC station to every CPU visible in the project, including the SINAMICS Integrated object under SIMOTION.

1. Open the SCOUT project, then open NetPro from the project navigator.
2. Identify the PG/PC station. If it does not exist, right-click the project and add a new PG/PC station with the same Ethernet interface as configured above.
3. Verify a subnet is attached to the PG/PC station and to the SIMOTION D CPU.
4. Select the S7 connection between PG/PC and SIMOTION CPU.
5. Open the Properties dialog for the SIMOTION CPU's PROFINET interface (X150 / X160 / IE1 / IE2, depending on D435 variant).
6. Confirm the S7 Online Access checkbox reads Active. The thick yellow line behind the thin green line in the NetPro graphic indicates that routing is enabled.
7. Save and compile NetPro, then download the configured connection to the SIMOTION CPU.

Enabling S7 Online Access on the SIMOTION CPU

The "Active" routing bit on the SIMOTION CPU interface must be enabled before any client (PG/PC, HMI, or another controller) can route through the CPU. In NetPro, double-click the SIMOTION CPU, navigate to the interface properties, and confirm that the routing bit is set:

1. Open SIMOTION CPU > Properties > Interfaces.
2. Select the Ethernet interface used by the controller on the plant network.
3. Tick S7 Online Access and confirm.
4. Recompile NetPro and download to the SIMOTION CPU.

If the checkbox is greyed out, the SIMOTION CPU is at an early firmware revision that does not yet expose the S7 routing attribute; upgrade the firmware to a current SIMOTION D V4.x or V5.x version where this attribute is configurable.

Memory Card, Firmware, and Hardware Configuration Download

When a SIMOTION D controller ships from the factory or has been reset to default firmware, the controller accepts a SIMOTION program download but does not yet contain the HW Config that exposes SINAMICS Integrated as a routable sub-node. SCOUT reports the connection error until the configuration is written to the controller at least once.

1. In SCOUT, open Target system > Download > Hardware configuration.
2. Wait for SCOUT to confirm the configuration is written.
3. Cycle the online state: Target system > Online > Cancel, then Online > Connect to target system.
4. Re-attempt the SINAMICS Integrated online connection.

If SCOUT continues to refuse the connection with the same error, the CFast or SD card on the SIMOTION D435 may be at fault. Power down the controller, remove and re-seat the memory card, then power up and re-download the configuration. Persistent corruption on the card requires replacement; Siemens specifies the card type and capacity in the SIMOTION D4xx operating instructions.

Recovering from Project Corruption

If the PG/PC interface, NetPro routing, and configuration download are all confirmed correct and the connection still fails, the project on the engineering workstation may be internally inconsistent. SCOUT projects stored on a Windows file system can become corrupted when the project database is interrupted mid-write (e.g., BSOD, power loss, antivirus quarantine of the project files).

1. Create a new SCOUT project.
2. Insert the SIMOTION D435 with the same order number and firmware version as the physical controller.
3. Insert SINAMICS Integrated from the catalog under the SIMOTION CPU.
4. Configure NetPro with the same subnet and PG/PC station as in the failed project.
5. Download the empty project to the SIMOTION controller.
6. Confirm that SINAMICS Integrated comes online in the new empty project.
7. If the drive comes online with an empty project, the issue was project corruption. Re-author the user program (MCC, ST, or LAD/FBD) and copy it back into the new project before commissioning.

This is the diagnostic recommended by experienced field engineers: an empty project with only hardware often resolves the routing problem when the original project is at fault.

Verification Procedure

After applying any remediation, perform the following verification sequence to confirm the SINAMICS Integrated online connection is restored:

1. Open Target system > Reachable nodes in SCOUT and confirm the SIMOTION CPU is listed.
2. Expand the SIMOTION CPU in the Lifelist and confirm SINAMICS Integrated appears as a child node.
3. Open the SCOUT project, right-click the SINAMICS Integrated object, and select Connect to target system.
4. Confirm the online dialog no longer returns "Error occurred while establishing a connection."
5. Open the drive's parameter view (Control Unit > Parameters) and confirm online values populate.
6. Read the drive diagnostics buffer (alarms) and confirm no F-class fault is present that would mask online access.

Diagnostic Checklist and Field-Proven Sequence

When the connection failure reoccurs intermittently, run through this checklist in order. Each step isolates one common cause.

Related Issues and Edge Cases

Several edge cases produce the same "Error occurred while establishing a connection" symptom and should be ruled out before deeper troubleshooting:

• Drive in fault state: If the SINAMICS Integrated carries an active F-class fault (e.g., F08501 PROFIBUS communication failure, F30002 DC link overvoltage), SCOUT may refuse the online connection to protect the drive from parameter writes during a fault. Clear the fault buffer first using the operator panel or a starter commissioning tool.
• PROFINET name assignment: On PROFINET variants of the SIMOTION D435, the integrated SINAMICS shares the device name of the SIMOTION CPU. If the device name on the controller does not match NetPro, routing to the integrated drive fails. Re-assign the PROFINET device name via Target system > Ethernet > Assign PROFINET device name.
• Firmware version mismatch: SCOUT 4.1.5.6 supports SIMOTION firmware V4.1.x and V4.2.x. Controllers at V4.0 or V5.x require a matching SCOUT version. Refer to the Siemens Product Support for the SCOUT/SIMOTION compatibility matrix.
• Integrated connection from WinCC Unified: The Siemens documentation for WinCC Unified lists the same configuration prerequisite: an integrated connection requires the PLC hardware configuration to define the HMI connection. If a TIA Portal HMI in the same plant also fails to reach a SIMATIC S7-300/400, the same routing/configuration interpretation applies (Causes of a faulty connection - RT Unified).
• Multiple PG/PC access points: On workstations with more than one STEP 7 / SCOUT version installed, the wrong access point (e.g., S7ONLINE (STEP7) -> ISO vs TCP/IP) is silently selected. Force the TCP/IP access point in the Set PG/PC Interface dialog before connecting.

Summary

The most common cause of "Error occurred while establishing a connection" when SCOUT connects to SIMOTION but not to SINAMICS Integrated is the absence of an S7 routing entry from the PG/PC station through the SIMOTION CPU. Enabling the S7 Online Access = Active bit on the SIMOTION CPU interface, downloading the HW Config at least once, and verifying the PG/PC interface assignment resolve the majority of cases. When all of these are correct, project corruption on the engineering workstation is the next suspect; rebuilding the project from a new template restores online access without changing the physical hardware. For deeper platform-level reference material and firmware-specific instructions, consult the Siemens Product Support portal.

Frequently Asked Questions