Resolving SINAMICS G120C All-Orange LED Initialization Fault: Firmware Recovery Procedure

The SINAMICS G120C compact inverter is widely deployed in conveyor, pump, fan, and basic servo-pump applications across the food-and-beverage, water/wastewater, and packaging industries. Like any embedded controller with a multi-MCU architecture (control unit + power module + optional safety card), the G120C can enter a non-recoverable initialization state when internal firmware becomes corrupt, parameter memory fails, or the safety firmware handshake is interrupted. This condition is recognizable on the Control Unit (CU) by a very specific LED signature: Ready, BF (Bus Fault), and Safe all glow steady orange/amber, the PROFINET link LEDs (L/A) remain green if a cable is plugged in, the BOP-2/IOP-2 operator panel latches into a "busy" or "init" state, and all communication channels (USB, RS-232, PROFINET) refuse to establish a connection.

This condition is the most common field-service problem on legacy SINAMICS G120C units that were last commissioned with STARTER V13 or STEP 7 V13 (TIA Portal) and lower. The standard commissioning flow on a healthy drive cannot recover from this fault because the drive never finishes POST to expose its PN interface. The only reliable recovery path is a memory-card firmware reload using an SD card inserted directly into the Control Unit's card slot, and only when this also fails is hardware replacement required.

1. Affected Product Range and Part Numbers

The condition applies to the G120C family with PROFINET and safety-integrated variants. Always confirm the part number on the rating label on the side of the Control Unit before ordering firmware.

The 6SL3210-1KE family is the most affected by this fault because it pairs a CU240E-2 with a PM240-2 power module in the field. The CU240E-2-PN-F variants are over-represented in failure statistics because they add a third firmware image (the safety firmware) that must handshake with the main firmware during boot. If any of the three images is corrupt or version-mismatched, the CU latches with all status LEDs amber.

2. LED State Decode for SINAMICS G120C

Understanding what each LED color means on a G120C is essential for correct diagnosis. The color/state tables below are derived from the official SINAMICS G120C operating instructions and Field Manual.

2.1 Ready LED (RDY)

2.2 Bus Fault LED (BF)

2.3 Safe (STO) LED

2.4 PROFINET Link LEDs (L/A1, L/A2)

The diagnostic signature reported by field service — Ready + BF + Safe all orange, PROFINET port LEDs green — is the canonical sign that the CU240E-2 has loaded its boot loader, but cannot complete the handshake to the main firmware and the safety firmware. The PROFINET PHY is powered from a separate supply rail that comes up before the firmware handshake completes, which is why the link LEDs work while the application firmware is still in boot-loader state.

3. Root Cause Analysis

The "all-orange" condition is the result of one or more of the following root causes, in order of field frequency:

1. Corrupt application firmware image on internal flash. Caused by interrupted firmware download (loss of 24 V supply during a STARTER or TIA Portal firmware update), EMC-induced flash corruption, or repeated power-cycling during commissioning with V13 SP1 or older.
2. Version mismatch between CU main firmware, safety firmware, and SD-card image. When a CU240E-2 PN-F is parameterized with a newer safety firmware than the application image, the safety handshake never completes and the CU latches into a wait state with all three LEDs amber.
3. Failed or missing parameter backup (EEPROM). Internal EEPROM stores the parameter set; if the EEPROM is corrupt, the boot loader cannot reconstruct the previous configuration and refuses to leave init state.
4. BOP-2 / IOP-2 plugged in and incompatible. A BOP-2 or IOP-2 with a firmware version newer than the drive's main firmware can hold the drive in a "busy" handshake loop. The drive never enters run state but the BOP displays "init" or "busy" indefinitely.
5. Failed CU hardware. Defective flash IC, defective SDRAM, or damaged CPLD/FPGA. In this case the firmware recovery procedure will not succeed.

4. Pre-Recovery Diagnostics

Before attempting a memory-card firmware reload, perform these checks to rule out simple causes and to confirm the fault signature.

4.1 Physical Inspection

1. Disconnect the drive from line power. Verify zero voltage at the input terminals with a CAT III 600 V meter.
2. Wait 5 minutes for DC-link discharge (CU LED will continue to run from the 24 V logic supply if external 24 V is wired).
3. Remove the operator panel (BOP-2 / IOP-2 / blind cover). Inspect the RJ45 connector on the back of the panel for bent pins.
4. Inspect the SD-card slot on the CU240E-2 for a foreign card. Remove any card already present and inspect it in a PC.
5. Inspect the CU240E-2 PROFINET ports for debris, broken latches, or cable damage.
6. Confirm that the 24 V logic supply to terminals X1.1 (P24) and X1.2 (M) is within spec: 24 V DC ±10% (21.6 V – 26.4 V) at a minimum of 0.5 A.

4.2 Power-Up Observation

1. With the operator panel removed and no memory card inserted, apply only the 24 V logic supply. Do not apply 400/480 V line voltage.
2. Observe the LED sequence over 60 seconds. A healthy CU240E-2 will go through a black → orange flash → green steady sequence on the RDY LED within 30–45 seconds.
3. If the drive shows Ready orange steady, BF orange steady, Safe orange steady (or yellow), and PROFINET link LEDs green (with cable connected), the fault signature is confirmed.

4.3 Operator Panel Check

Connect a known-good BOP-2 (e.g., 6SL3255-0AA00-4BA1) or IOP-2 (6SL3255-0AA00-4JA1). If the panel also displays "init" or "busy" indefinitely, the firmware is confirmed corrupt. A panel that briefly shows the drive name then displays "----" indicates the firmware finished initialization but the safety handshake is failing — pointing to safety firmware corruption.

4.4 USB and RS-232 Check

The USB port on the CU240E-2 (X3) is powered by the main firmware. If the drive never reaches the application-firmware-ready state, the USB port will not enumerate on a host PC. Confirm on the host PC using Device Manager (Windows) or lsusb (Linux) — the Siemens device with VID 0x0908 and PID 0x0100 (SINAMICS USB) will not appear. This is a fast negative test.

5. Firmware Recovery via Memory Card

This is the recommended recovery path for a G120C that has a corrupt main or safety firmware. The procedure uses an SD card inserted into the CU's card slot to push a fresh firmware image into the internal flash. The same procedure is documented in the SINAMICS G120C Field Manual and the Siemens support portal.

5.1 Required Materials

5.2 Acquiring the Firmware Files

1. Open support.industry.siemens.com.
2. Search for the exact MLFB of the Control Unit (e.g., 6SL3244-0BB12-1PA1).
3. Navigate to Downloads and filter by Firmware.
4. Download the latest firmware package for the CU240E-2 PN-F. Current long-term support versions are typically in the V4.7 SPx and V5.x firmware streams. Note: do not downgrade below the firmware that was originally running unless the power module compatibility table explicitly permits it.
5. Unzip the package. The firmware image for the CU240E-2 PN-F is typically named FW_CU240E2_PN_F_Vxxxx.bin or appears as a folder with the same base name.

5.3 Preparing the SD Card

1. Insert the SD card into the PC.
2. Format the card as FAT32 with default allocation unit size. Do not use exFAT; the CU240E-2 boot loader does not recognize exFAT.
3. Copy the firmware files to the root directory of the SD card. Do not place them in a subfolder.
4. Eject the SD card safely from the OS.

5.4 Loading Firmware via SD Card

1. Ensure the drive is de-energized. 24 V logic supply must be present; line voltage does not need to be applied.
2. Insert the SD card into the CU240E-2 card slot, contacts facing down, label side up, until it clicks.
3. Apply the 24 V logic supply.
4. Observe the RDY LED. Within 5–10 seconds it should begin to flash green at ~0.5 Hz, indicating the firmware download is in progress.
5. The download takes 2–6 minutes depending on firmware size and SD card speed. Do not remove the card or remove 24 V during this process.
6. When the download completes, the RDY LED will either:
   • Flash red briefly and then go green steady (success), or
   • Flash red rapidly and stay red (firmware mismatch or corrupt image).
7. Remove 24 V, wait 30 seconds, then re-apply 24 V to boot from the new firmware.

5.5 Verifying Successful Recovery

1. After re-applying 24 V, the RDY LED should turn green steady within 30–45 seconds.
2. Insert a BOP-2 / IOP-2. The panel should now display the drive's current firmware version in r0018 or via the operator panel menu.
3. Connect a USB cable from the host PC to the CU's USB port. The PC should enumerate the device and STARTER / TIA Portal V15.1 or higher should be able to establish an online connection.
4. Connect PROFINET and verify that the IO controller can see the drive in its topology scan.

6. Firmware Compatibility Matrix

When choosing a target firmware version, verify compatibility with the installed Power Module (PM240-2) and any attached safety configuration. Mismatched firmware can result in F0135 / F07860 / F08501 faults after recovery.

7. Alternative Recovery Methods

If the SD card procedure does not recover the drive, work through the alternatives in order.

7.1 Web Server Access via PROFINET

Some CU240E-2 PN-F firmware versions (V4.7 SP3 and later) expose an internal web server on port 80 once the basic network stack comes up, even if the application firmware fails to fully boot. Set the PC to a fixed IP address in the 169.254.x.x range and connect directly to the CU's PROFINET port 1. Try https://169.254.1.1 in a browser. If the web server is reachable, you can pull a parameter dump and may be able to push firmware via the web interface.

7.2 Direct PC Connection with STARTER

Install STARTER V5.4 SP1 (or TIA Portal V15.1 or higher) on the host PC. Connect via USB and use Accessible nodes. Even when the drive appears offline, STARTER may detect the boot-loader. Use Target system → Firmware update from the menu to push a known-good firmware image.

7.3 Fieldbus Recovery via TIA Portal

Some firmware versions support a "firmware update via PROFINET" mode accessible from TIA Portal. Right-click the drive in the device view, select Online & Diagnostics → Firmware Update. This path requires the IO controller to be reachable and the drive to be in boot-loader state.

7.4 Hardware Replacement Decision

If all three methods above fail, the CU is almost certainly hardware-defective. Field data shows this is the case for fewer than 10% of "all-orange" incidents, but it does happen. Replace the Control Unit only — the Power Module (PM240-2) is unaffected and does not need replacement. Transfer any safety-related configuration parameters from the replacement CU's commissioning record, or re-commission with the saved project.

8. Verification Procedure

Once the drive has been recovered (either by firmware reload or CU replacement), perform the following verification sequence before returning the drive to production service.

1. Parameter integrity check: Connect STARTER / TIA Portal and read out r0018 (firmware version), r0019 (DRIVE-CLiQ component version), r0127[0] (power module type), and r9771[0..19] (CU serial number). Confirm these match the drive's documentation.
2. Fault buffer clear: Read out the fault buffer r0947[0..7] and r2123[0..7]. Document any historical faults. Clear the buffer with p3981 = 0 → 1 transition (acknowledging via digital input).
3. Safety function test (if PN-F variant): Verify STO response time, verify safety input wiring, run the safety acceptance test per the SINAMICS Safety Integrated Function Manual.
4. PROFINET IO test: Assign the device name and IP from the IO controller. Run the topology scan. Confirm cyclic IO exchange.
5. Motor identification run: With the motor decoupled or unloaded, perform a stationary motor identification (p1910 = 1) followed by a rotating measurement if possible (p1960 = 1).
6. Burn-in: Run the drive under no-load for 30 minutes. Monitor temperature, output current, and DC-link voltage r0026.

9. Preventive Measures

To prevent recurrence of the "all-orange" condition after recovery, apply these field-proven practices.

• Use the latest TIA Portal / STARTER on all engineering stations. TIA Portal V13 SP1 and earlier are known to produce parameter sets that can corrupt CU flash on certain CU240E-2 firmware versions. Upgrade to TIA Portal V17 or higher.
• Always commission firmware updates via SD card rather than over PROFINET for production-critical drives. SD-card updates are atomic; PROFINET updates can be interrupted by network issues.
• Power-quality survey: Install a 24 V DC UPS or a power-conditioner on the 24 V logic supply. Brownouts and surges on the 24 V rail are a leading cause of flash corruption.
• Maintain a backup SD card with the latest known-good firmware for every drive on site. Label the card with the MLFB, firmware version, and date.
• Document parameter sets in the project archive. STARTER and TIA Portal both support *.par and *.dcmp parameter files; store these on the engineering server, not just the local workstation.
• Verify EMC installation per the SINAMICS G120C EMC installation guidelines. Improper cable routing and missing cable shields are a documented cause of corrupted flash memory.

10. Troubleshooting Matrix

11. Frequently Asked Questions