Fanuc alarm 900: ROM PARITY
system alarm · Fanuc 0i-D
What it means
Parity error detected in CNC/macro/servo flash ROM during boot; FROM contents corrupt or FROM hardware failing
Likely causes
- FROM (flash ROM) data corruption
- degrading FROM memory cell(s)
- main board memory controller fault
Triage note: Try full memory clear (RESET+DELETE at power-on) and reload system software first; recurring 900 = hardware, replace FROM module or main board
Replacement parts
We supply the following units for this alarm — tested, warranty-backed:
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A20B-8200-0740
Main CPU Board (0i-D) · Common cause
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A20B-3300-0313
FROM/SRAM Module (16i/18i/21i) · Primary suspect
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A02B-0303-B802
Main CPU Board (30i/31i-B) · Common cause
Need the part urgently?
Send us alarm 900 with your machine details — typical RFQ turnaround is 24–48h.