Resolving S7-1200 CPU 1217C SF Fault LED with V90S Drive

1. Problem Overview

An S7-1200 CPU 1217C is being used as the controller for a SINAMICS V90S servo drive, networked through a SCALANCE X005 unmanaged/lightly-managed industrial Ethernet switch. The CPU reports a diagnostic status flagged by the thermometer icon in the TIA Portal device view, the module is listed as faulty in the project tree, and the SF (System Fault) LED on the front of the CPU is active. Communication between the controller and the drive is not established.

The thermometer icon and "faulty" module status are TIA Portal's high-level indicators that the PLC has raised an entry in its diagnostic buffer. They are not a diagnosis in themselves; they are a pointer to a specific event the CPU has logged. The actual cause must be extracted from the diagnostic buffer and from the topology view before any corrective action is taken.

2. Component Identification and Catalog Numbers

Confirm the exact part numbers in your hardware catalog before proceeding, because firmware compatibility, GSDML versions, and telegram support all depend on the precise variant.

The 1217C is the top-end S7-1200 CPU. It has two PROFINET interfaces: the top X1 port (PN/IE) and the bottom X2 port. When a switch sits between the controller and a V90S, the typical topology is CPU 1217C X1 → SCALANCE X005 → V90S X150. A common error is to assume X1 and X2 can be used identically; X2 is software-configurable as a second PROFINET port only with firmware 4.4 or higher.

3. What the SF LED and Thermometer Icon Mean

Per the Siemens Status LEDs documentation for the SIMATIC S7-1200 manual collection, the front-panel LEDs of an S7-1200 CPU include the following diagnostic indicators:

The thermometer icon shown in the TIA Portal online & diagnostic tools corresponds to the "diagnostic status available" symbol. It appears for any device whose DS0 / DS1 channel diagnostics are flagged. For an S7-1200 acting as a PROFINET IO controller, this almost always points to a connected IO device that is not in data exchange — the most likely candidate being the V90S.

4. Initial Diagnostic Procedure

Follow this sequence before changing any hardware, project, or parameter:

1. Establish online connectivity. In TIA Portal, select the CPU 1217C in the project tree, then click Go online (or press Ctrl+Shift+M). Use the configured PG/PC interface (PROFINET or Ethernet adapter).
2. Open Online & Diagnostics. Right-click the CPU → Online & Diagnostics → select the device from the list of accessible nodes.
3. Read the diagnostic buffer. Navigate to Diagnostics → Diagnostic buffer. Sort the entries by Time stamp descending. The most recent entry is the current fault; events above it are the chain of causes that led to it.
4. Export the buffer. Click Save as text file and keep a copy. This is your evidence trail and will be required if you open a Siemens support request (SR).
5. Open the topology view. In the project tree, select the PROFINET subnet and open Topology view. Click Compare offline / online. The comparison highlights every port, cable, and device that does not match the offline configuration.
6. Check the V90S directly. If you have the SINAMICS V-ASSISTANT or TIA Portal access to the V90S, connect to it and read Online → Diagnostics → Message buffer. Capture the active fault code (F-code) and the warning code (A-code).

5. Reading the Diagnostic Buffer

The S7-1200 diagnostic buffer holds the last 100 events. Each event has an Event ID, a hex-coded value that identifies the cause. Below are the most common Event IDs you will see for a V90S-on-PROFINET failure, in descending order of frequency:

For each event the diagnostic buffer also shows the IO device address, the slot, and (for slot-level events) the channel and channel number. The IO device address must match the IP address and device number of the V90S as configured in the project.

6. Determining the V90S Variant: PN or USS/PTI

Before any PROFINET-specific check, you must confirm the variant of the SINAMICS V90S in the cabinet. The V90 family has two communication options that look identical from the front:

The two variants have different catalog numbers, different firmware, and different GSDML files. If the project tree shows a PROFINET device node for a V90S, but the physical drive is a V90 PTI, the controller will never reach data exchange and the SF LED will latch.

To verify, look at the V90S nameplate. The article number ending in U (PROFINET) versus A (pulse/analog) tells you which device is in the cabinet. If the wrong one was ordered, swap the device; do not attempt to "force" the project to match.

7. PROFINET Communication Path Verification

Once the variant is confirmed as PROFINET, walk the protocol stack from bottom to top.

7.1 Physical Layer

• Cable category: at least Cat 5e SF/UTP, 100 Ohm, for industrial PROFINET. The recommended cable is PROFINET Type C (fixed installation) or Type B (flexible). Avoid standard office patch cables beyond 5 m in industrial cabinets.
• Maximum segment length: 100 m end-to-end between two devices, 100 m between switch and device. SCALANCE X005 is a 100 Mbps switch, so the 100 m rule applies per segment.
• Connector pin-out: PROFINET RJ45 uses pins 1, 2, 3, 4, 5, 6. Pins 7 and 8 are reserved for power over Ethernet and are not used by S7-1200 / V90S.

7.2 Port LEDs on the SCALANCE X005

If the port LED facing the V90S is dark, the problem is physical (cable, connector, or power to the drive). The SF LED on the CPU is a symptom, not the cause.

7.3 IP Address and Device Name

PROFINET requires a unique IP address and a unique device name on the subnet. The V90S ships with a default name of v90-pn and IP 0.0.0.0. The PLC will not bring it into data exchange until:

1. A device name has been assigned to the V90S via Topology → Assign PROFINET device name, or via the V90S BOP (Basic Operator Panel) under Menu → Setup → PN → Name.
2. The IP address is set in the same range as the CPU 1217C. Common practice: CPU 1217C = 192.168.0.1, V90S = 192.168.0.2, mask 255.255.255.0.
3. The IP and name match the entries in the TIA Portal project tree under Devices & Networks → [V90S node] → Properties → Ethernet addresses.

7.4 Topology Editor — Compare Offline / Online

The TIA Portal Topology editor allows you to define, port-by-port, which PROFINET port of which device connects to which other port. If you have not defined the topology, TIA will still bring up the network, but the Compare offline / online function will show a "no port interconnection defined" warning.

To run a comparison:

1. Open Devices & Networks → Topology view.
2. Click the Compare offline / online button in the toolbar.
3. TIA Portal will run LLDP discovery on every port and report the actual physical neighbor of each port.
4. Any port whose neighbor does not match the offline configuration is highlighted in red.

Common mismatches:

• Cable plugged into the wrong port of the SCALANCE X005 (e.g., port 1 instead of port 3).
• Two PROFINET devices with the same port number assignment.
• SCALANCE X005 not yet in the project, so the offline editor shows an open-ended link; online LLDP shows the actual switch.

8. V90S Telegram and Configuration

The V90S uses Siemens-standard PROFIdrive telegrams. The most common selections are:

The telegram selected in the V90S parameter P0922 must match the telegram selected in the TIA Portal device configuration under V90S → Properties → Module parameters → Telegram. A mismatch raises Event ID 0x001E in the diagnostic buffer of the CPU.

Additional V90S parameters that must agree with the controller project:

• P0922 — PROFIdrive telegram selection.
• P0925 — Number of PROFIdrive telegrams (usually 1).
• P0970 — Reset to factory (only use if drive is in known-good state).
• P2030 — Fieldbus node address (typically 0; IP/name come from PROFINET, not from P2030).

9. Firmware and GSDML Compatibility

A V90S firmware that the TIA Portal GSDML cannot interpret will not bring up a PROFINET AR, and the CPU will report the device as faulty. The V90S firmware history is in the 5SE series; current field releases are in the 1.04.x range. Always check:

1. The GSDML file installed in TIA Portal: Options → Manage general station description files (GSD) → confirm the latest V90S GSDML is installed.
2. The V90S firmware: visible at Online → Drive unit → Version overview in Startdrive, or on the V90S BOP under Menu → Setup → Drive info → Firmware.
3. Whether Startdrive (≥ V16 for V90S) is installed on the engineering station.

For the CPU 1217C, firmware 4.4 or higher is required to use the second PROFINET port X2. The SCALANCE X005 supports LLDP and is transparent to PROFINET RT, so it requires no firmware of its own; the field-relevance is the link speed (100 Mbps full duplex) and auto-negotiation behavior.

10. Step-by-Step Resolution Procedure

Apply the following in order. Stop and capture results after each step; do not batch.

1. Read the diagnostic buffer and note the most recent Event ID and IO device address.
2. Verify the V90S variant (PN vs PTI) by part number on the nameplate.
3. Power-check the V90S: 24 V control voltage, 3-phase or 1-phase power depending on the 200 V / 400 V variant, and the green "RDY" LED on the V90S should be steady green within 3 s of power-up.
4. Check the SCALANCE X005 port LEDs. The port facing the CPU and the port facing the V90S should both show a green link LED.
5. Confirm the V90S has a device name via the BOP or via Topology → Assign PROFINET device name in TIA Portal.
6. Confirm the V90S IP via the BOP or via the online accessible nodes in TIA Portal.
7. Run topology compare offline/online and resolve any red mismatches.
8. Compile and download the project to the CPU 1217C.
9. Power-cycle the V90S (24 V control voltage off-on, not the main power) to force AR re-establishment.
10. Re-read the diagnostic buffer. The SF LED should extinguish within 5 s of the AR establishment if the previous cause has been resolved.

11. Verification

After the resolution, run a functional verification:

1. Online status check. In TIA Portal, go online with the CPU. The V90S node should show green in the device view, not red. The thermometer icon should be gone.
2. LED check. CPU 1217C: RUN = green solid, ERROR = off, MAINT = off, SF = off. V90S: RDY = green solid, BF (Bus Fault) = off. SCALANCE X005: link LEDs on active ports = green.
3. Process data test. In a watch table, force a speed setpoint to the V90S via the PROFIdrive word NSOLL (Standard Telegram 1) and confirm the actual value NIST follows within the configured ramp time. This confirms bi-directional PROFINET IO data exchange.
4. Diagnostic buffer check. The diagnostic buffer should be free of new PROFINET-related Event IDs. A clean state has the most recent entry being a "PROFINET IO device return" (Event ID 0x015A), then nothing newer for at least 5 minutes.

12. Troubleshooting Matrix

13. Common Pitfalls

• Confusing PTI with PN. The V90S lookalike PTI variant has no PROFINET interface; it has RS485 and analog I/O. The only way to PROFINET a V90 is to have the PN variant on the nameplate.
• Reusing an old project with a new drive. A project made for a V90 PN with firmware 1.00 will compile against a V90 PN with firmware 1.04, but the slot list may differ. Always re-import the GSDML and re-do the slot configuration when the drive firmware is upgraded.
• Forgetting the device name. The V90S will respond to PING with its default name v90-pn and the IP that was last assigned, but it will not enter data exchange until the name matches the project.
• Routing through the wrong port. The CPU 1217C's lower PROFINET port X2 is disabled by default and only available from firmware 4.4 with a configuration in the device properties. The default project uses X1 only.
• SCALANCE X005 not in the project. The switch does not need to be a PROFINET device in the TIA Portal project; the topology editor will still discover its LLDP neighbors. A "Compare offline / online" that flags the switch as missing is a configuration hygiene issue, not a fault.

14. Frequently Asked Questions