Citroen Saxo KM Calibration - ECU EEPROM IMMO Service Tool 2025-09-16

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• Purpose: Write a calibrated KM value to Saxo clusters via a standard COM (sеriаl) port.
• Interface: Any USB-to-sеriаl adapter that creates a COM port — no J2534 or special hardware needed.
• Workflow: Open COM port → enter new KM → Write KM → Close COM port. That's it.
• OS: Windows 7 through 11 (32/64-bit); tested on Win 10 LTSC 2019.

• Bench power is critical. Feed the cluster a stable 12 V from a bench supply or battery with support — a voltage dip mid-write can corrupt the EEPROM.
• Back up first. If you have a programmer (e.g. XPROG, Orange5, or even a cheap CH341A for the external EEPROM), dump the original data before touching anything. If the write goes wrong you'll want a rollback path.
• Correct COM port. If the tool doesn't see the cluster, double-check Device Manager for the actual COM number assigned to your USB-sеriаl adapter. Some adapters need the FTDI or CH340 driver installed manually.
• Cluster-specific only. This targets the NEC-780826-GC variant. Other Saxo/AX clusters (e.g. older Jaeger or Magneti Marelli units) use different MCUs and won't respond.