Hi,

What do you think of chatgpt response to this question :

Give me examples how Immo Off Software modify eeprom data ?

chatgpt response :

Example 1: Zeroing Out Key Data

In many immobilizer systems, the EEPROM stores key/transponder data in specific memory locations.
Original EEPROM Data:

0x100: 12 34 56 78 90 AB CD EF FF EE DD CC BB AA 99 88


After Immo Off:

0x100: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00




  • What Happened?The software erased the key/transponder data stored in these memory locations. The immobilizer now has no keys to verify, so the ECU will no longer require key authentication.

Example 2: Disabling Immobilizer Flags

Many immobilizer systems use specific bits or flags in the EEPROM to indicate whether the immobilizer is enabled.
Original EEPROM Data:

0x200: 01 00 00 00 45 67 89 AB


After Immo Off:

0x200: 00 00 00 00 45 67 89 AB




  • What Happened?The first byte (0x01) might represent the immobilizer status (01 = Enabled). The software changes it to 0x00 to disable the immobilizer.

Example 3: Overwriting Immobilizer Configuration

Some ECUs store immobilizer configurations in specific memory blocks.
Original EEPROM Data:

0x300: FF FF 12 34 56 78 90 AB CD EF 00 11 22 33 44 55


After Immo Off:

0x300: FF FF FF FF FF FF FF FF FF FF 00 11 22 33 44 55



  • What Happened?The immo off software overwrote a specific range of bytes (12 34 56 78 90 AB CD EF) with FF values, disabling the immobilizer-related configuration.

Example 4: Editing Checksum Data

To ensure the ECU operates correctly after modifying EEPROM data, the checksum value (used to verify data integrity) must often be recalculated and updated.
Original EEPROM Data:

0x3F0: AA BB CC DD EE FF 12 34
0x3FF: 56 78 90 AB (Checksum: 90 AB)


After Immo Off:

0x3F0: AA BB CC DD EE FF FF FF
0x3FF: 34 12 78 90 (Checksum: 78 90)



  • What Happened?
    • Some data (12 34) was modified to disable the immobilizer.
    • The checksum (90 AB) was recalculated and updated to match the new data, ensuring the ECU recognizes the EEPROM as valid.

Example 5: Disabling Challenge-Response Logic

Some ECUs store challenge-response logic in EEPROM. Immo off software modifies these sections to skip the verification.
Original EEPROM Data:

0x400: A1 B2 C3 D4 E5 F6 01 02 03 04 05 06 07 08


After Immo Off:

0x400: A1 B2 C3 D4 E5 F6 FF FF FF FF FF FF FF FF



  • What Happened?The software overwrote the challenge-response section (01 02 03 04 05 06 07 08) with FF values, effectively bypassing the cryptographic verification.

Tools for Verification

  • Hex Editors: Tools like HxD allow you to visually inspect and compare original and modified EEPROM dumps.
  • Immo Off Software: Programs such as ECU Titanium or IMMO Universal Decoding display the changes applied to the EEPROM.
  • Checksum Calculators: Many immo off tools include built-in checksum calculators or require separate tools to verify checksum integrity.