Repeated reads that produce different files need an explanation before either is treated as a trustworthy original. Some data may legitimately change with operation, while unexpected differences can also reflect the read method, connection or unsupported access.
Preserve both results
Keep the files unchanged with timestamps, operation names and logs. Record whether the unit was powered or used between reads and whether the tool reported warnings. A simple file comparison shows a difference; it does not explain why that difference exists.
A competent specialist should identify which regions were read and what changes are expected for that controller. Do not repeatedly write one result back merely to see whether the next read matches. If the unit is still functioning, avoid turning an uncertain backup into a new fault. Send the module identification and original logs with the enquiry, and ask for the limits of any proposed recovery route to be stated before modification.
Related help
- ECU EEPROM Emulation: Why There May Be No Separate Memory Chip
- ECU Flash and Calibration Data: Why File Size Does Not Prove Completeness
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