Lenovo MT 1842 Manual page 76

FRU replacement notices
3. To write ECA information, select 1. Write ECA/rework
number from EEPROM, and follow the instruction.
4. To write box build date, select 4. Write box build date
from EEPROM, and follow the instruction on the
screen.
If the system board is being replaced, try to read the ECA
information from the old system board and transfer the
information to the new system. If the system board is
inoperable, this will not be possible.
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R50e and R52 Series