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FANUC Alarm ARC-040 — STOPL Missing I/O: …

Manufacturer wording — STOPL Missing I/O: %s^1 (%s^4,%d^5)
The manual prints placeholders; your controller fills them in with the real group, axis or number.

FANUC ARC-040 (“STOPL Missing I/O: …”): The named weld I/O signal is not detected or configured properly. First check: Verify the I/O hardware is connected and the signal is assigned a port number in the Weld I/O screen.

Updated 2026-09-17 · LogrobotLM reference

Description

The named weld I/O signal is not detected or configured properly.

Remedy

Verify the I/O hardware is connected and the signal is assigned a port number in the Weld I/O screen. Use the CONFIG function key if the signal is unassigned.

Related codes

ARC-038STOPL Already held another equipmentARC-039STOPL … AO is not scaledARC-041STOPL Weld EQ needs DeviceNet optionARC-042STOPL Weld EQ needs Expl Msg option

Indicative field information — the robot manufacturer's manual and safety procedures always prevail. Never bypass a safety device; apply lockout/tagout (LOTO) before any physical intervention. How this reference is built →