SINAMICS G120C EEPROM Save Failure: F01002 Recovery Guide

1. Problem Overview

The SINAMICS G120C is a compact, modular frequency inverter from Siemens (frame sizes FSA through FSE; 0.55 kW to 132 kW). It uses a Control Unit (CU) of the CU230P-2, CU240B-2, CU240E-2, or CU250S-2 family. The Control Unit contains two non-volatile storage areas: the internal ROM (EEPROM) on the device and an optional removable memory card (SD/SDHC).

Two failure modes are repeatedly observed in the field:

1. Parameters do not persist after a power-off/power-on cycle. Changes made through the BOP-2 (Basic Operator Panel), IOP-2 (Intelligent Operator Panel), SINAMICS Startdrive in TIA Portal, or STARTER are lost on reboot.
2. After a firmware downgrade (e.g., from V4.6 to V4.5), the drive remains in an inoperable state. The RDY LED and the BF LED flash slowly red, and subsequent memory card operations return fault F01002 — Internal software error.

2. Root Cause Analysis

The CU2xy-2 family uses two physically separate non-volatile areas: the on-board EEPROM for parameter sets, and the firmware flash, which is loaded into RAM at boot. Save to EEPROM copies the volatile parameter image (RAM) into the EEPROM using parameter p0971 or the equivalent menu action on the BOP-2 / IOP-2.

3. Required Tools and Prerequisites

• Siemens SINAMICS G120C Operating Instructions (latest edition for the CU variant installed)
• STARTER V5.x or SINAMICS Startdrive in TIA Portal (version must support the G120C firmware installed)
• BOP-2 (6SL3255-0AA00-4CA1) or IOP-2 (6SL3255-0AA00-4JA1) for offline parameter access
• Siemens-branded or SanDisk industrial SD/SDHC card, ≤ 2 GB for legacy FW or up to 32 GB SDHC for newer CU2xy-2 firmware. Format FAT16/32
• Firmware files from Siemens Product Support: support.industry.siemens.com — search "G120C firmware". Verify the file set includes the matching CU type (e.g., 6SL3246-0BA22-1FA0 for CU240E-2 PN V4.6)
• USB cable (Mini-USB on CU) or PROFINET connection for commissioning PC

4. Diagnostic Procedure

1. Read out the fault buffer. Connect with STARTER/Startdrive → project tree → drive → Diagnostics → Fault/alarm buffer. Note the exact fault number, time stamp, and any associated value (r0949).
2. Check the firmware version on the CU. With BOP-2, navigate to r0018 (firmware version) and r0020 (firmware version, long). With the IOP-2 use the Diagnostics → Drive Information menu. Confirm that commissioning software version is compatible.
3. Verify the current ROM contents. With the BOP-2 in Menu → Parameter backup/restore, check whether the last saved parameter set matches the active RAM. A mismatch confirms the EEPROM is not being written.
4. Inspect the memory card. If a card is inserted, browse to \USER\SINAMICS\<CU_article_no>\. The folder must match the target CU. Older parameter sets that were saved on a different CU variant will trigger F01002 when restored.
5. Monitor LED states. Reference LED pattern table:

5. Step-by-Step Recovery Procedure

Step 5.1 — Power-Cycle After Firmware Update

If the RDY and BF LEDs are flashing slowly red after a firmware transfer, this is the documented handshake. The inverter is signalling that the new firmware has been staged and a power reset is required to commit it.

1. Disconnect the 24 V control voltage and the line voltage.
2. Wait ≥ 30 seconds to allow the internal bulk capacitors to discharge below the undervoltage lockout (the CU230P-2 monitors U_DC; below ~50 V the flash controller releases the boot latch).
3. Re-apply 24 V and line voltage. Observe the LED sequence: RDY should transition from solid red → slow green flashing → solid green (or solid orange during pre-charge, depending on frame size).
4. If the LEDs return to slow red flash on BF/RDY, the staged firmware is invalid — proceed to Section 5.3.

Step 5.2 — Save Parameters to EEPROM (Copy RAM to ROM)

Parameter changes are stored in volatile RAM by default. They must be explicitly committed to the non-volatile EEPROM using parameter p0971.

1. From STARTER / Startdrive: Online → Drive → Commissioning → Copy RAM to ROM. Wait for the progress bar to complete and the acknowledgement bit r3996.0 to return to 0.
2. From BOP-2: MENU → Parameter save → Save to EEPROM → OK. The BOP displays “Save in progress”; do not power off for at least 10 s after the BOP returns to the status screen.
3. From IOP-2: Menu → Parameter backup → Save parameter set in drive.

Alternative direct write (only if you cannot access a commissioning tool): set p0971 = 1 and press P on the BOP-2. The drive will write the entire parameter set to EEPROM within 3–6 s; the RDY LED remains red during the write.

Step 5.3 — Factory Reset and Clean Re-flash

Use this when F01002 is active or the ROM image is suspect. It clears the EEPROM and re-stages firmware.

1. Set p0010 = 30 (commissioning filter = factory reset) and p0970 = 1 (factory reset). Acknowledge any faults first.
2. Wait until p0970 returns to 0 (reset complete). The drive restores the as-shipped parameter set.
3. Cycle power to apply factory defaults.
4. If the drive is in a state where STARTER cannot go online (e.g., BF/RDY flashing red), perform a firmware re-flash via memory card:
   • Copy the firmware BIN files (e.g., SLM_G120C_CU240E2PN_V04_06_02_00.bin) to the memory card root.
   • Insert the card into the CU with the drive powered OFF.
   • Power ON. The CU detects the new firmware and performs the same staged-load handshake as in Section 5.1.
   • Power cycle again after the LEDs indicate the update is complete.

Step 5.4 — Memory Card Restore Procedure

If a memory card backup exists, restore it after a clean firmware load:

1. Confirm the folder name on the SD card matches the target CU's article number (e.g., 6SL3246-0BA22-1FA0).
2. Insert the card. Power on the drive.
3. From BOP-2: MENU → Parameter backup → Restore from SD card. Wait for the acknowledgement; do not interrupt power for at least 15 s after the prompt disappears.
4. From STARTER/Startdrive: Online → Drive → Parameter backup → Restore from memory card.

If F01002 returns immediately when the card is inserted, the data on the card is from a different CU variant or the card's filesystem is non-standard. Re-format the card as FAT32, copy the backup from a known-good drive of the same article number, and retry. If F01002 persists with a verified-good card, the on-board EEPROM is hardware-faulty and the Control Unit must be replaced.

6. Firmware Update Best Practices

• Always match the firmware set to the CU article number (printed on the front label). Mismatched sets are a leading cause of F01002.
• Perform the update with a stable 24 V supply and a fully charged DC link. Use a UPS on the line side if the panel is subject to brown-outs.
• For STARTER/Startdrive updates, ensure the Web server password has been set (where applicable) and that the project is in Online mode before clicking Load to target system.
• For SD-card updates, the file order on the card is interpreted by the loader. Do not mix firmware from two different CU families on the same card.
• Always execute a Copy RAM to ROM immediately after the drive is recommissioned, otherwise the new commissioning parameters will be lost on the first power cycle.

7. Verification Checks

1. Power-cycle test: Make a non-default parameter change (e.g., ramp time p1120 from 10 s to 5 s), execute Copy RAM to ROM, wait 15 s, power OFF for 60 s, power ON. Verify the value is still 5 s by reading r0025 or by scrolling the BOP.
2. Fault buffer clear: Read r0945[0..7] and confirm no active F01002 entries. If any remain, repeat Section 5.3.
3. Memory card round-trip: Insert a freshly written SD card backup, power cycle, and confirm the parameters restore automatically (this is the default behaviour when a valid backup is detected at boot).
4. BOP/STARTER parity: Read the same parameter from BOP-2 and from STARTER/Startdrive online view. The two values must agree to within one refresh cycle.

8. When to Replace the Control Unit

Replace the CU if any of the following is true:

• F01002 persists after a verified-good firmware re-flash on a properly formatted card.
• The drive loses parameter values on every power cycle despite an observed Copy RAM to ROM completion (r3996.0 = 0).
• The RDY LED is steady red at power-up with no LED activity from BF, indicating a failed boot ROM.
• The drive has been in service for > 10 years in a high-temperature (> 50 °C ambient) panel and the EEPROM write cycle counter (read via p0441-related diagnostics where available) is at end-of-life.

Replacement procedure: power OFF, remove the CU from the Power Module (the CU slides off the PM after the four screws are loosened and the two front connectors are released), install the new CU, re-flash the firmware to match the panel's commissioning, and re-load the parameter backup. Do not mix CUs across different frame sizes (FSA through FSE) without verifying PM compatibility — the CU is universal, but the Power Module's firmware for the IGBT stack is loaded by the CU at first boot.

9. Quick Reference: Key Parameters and Fault Codes

10. Related Documentation

• SINAMICS G120C Operating Instructions (Siemens Industry Online Support)
• SINAMICS G120 / G120C Parameter Manual
• SINAMICS G120 / G120C List Manual (Parameter List)
• SINAMICS Startdrive in TIA Portal — Commissioning Manual
• Siemens Application Note: "Data storage for CU2xy-2" — internal memory (RAM/ROM) and memory card handling for the CU2xy-2 family

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