Fanuc alarm L: I/O LINK ERROR (unit LED)
PMC/I-O Link alarm · Fanuc Power Mate
What it means
On I/O Link slave units such as the Power Mate / Beta-series I/O Link servo unit, the 7-segment LED shows 'L' when a FANUC I/O Link error occurred - specifically when a unit connected to the line was turned off or dropped off the link. The slave keeps indicating the condition locally even if the master side reports its own alarm.
Likely causes
- Another unit on the I/O Link lost 24V power
- Link cable disconnected between units
- Master-side controller reset or failure during transfer
Triage note: LED indication applies to A06B-6093-H15x/H17x Beta I/O Link servo units; clear by restoring the missing unit/power and resetting the link.
Replacement parts
We supply the following units for this alarm — tested, warranty-backed:
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Offending I/O Link unit or link cable
i-o-unit · Common cause
Need the part urgently?
Send us alarm L with your machine details — typical RFQ turnaround is 24–48h.