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How do I fix an F40 (Device Unknown Fault) code for a 9000X Series drive?

A device unknown fault predominately happens when replacing boards in a drive. What this fault is looking for is valid data in the EEPROM on the circuit boards. This fault usually comes from the power board but the fault history should tell you what module and sub-module that is not valid. If this fault comes up without any work being done to the unit it means that some data has been lost by the board in question. You may be able to reprogram the board and get it to work but the board should probably be replaced at the earliest convenience as it is likely to happen again. If this happens after a board has been replaced it is likely that the correct data has not been loaded to the board. On drives that have multiple ASIC boards all the extra data needs to match from one unit to another. Please not that a star coupler board has to have a serial number programmed in it to make it work.