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FANUC Alarm APSH-121 — WARN can't write signal %s

FANUC APSH-121 (“WARN can't write signal %s”): The WRITE IO MACRO was called but the signal could not be found. First check: Check the MACRO call in the TP program.

Updated 2026-08-29 · LogrobotLM reference

Description

The WRITE IO MACRO was called but the signal could not be found. WRITE IO(signal name string, integer register number)

Remedy · Remède

Check the MACRO call in the TP program.

Frequently asked · Questions fréquentes

What does FANUC alarm APSH-121 mean?
FANUC APSH-121 (“WARN can't write signal %s”): The WRITE IO MACRO was called but the signal could not be found. WRITE IO(signal name string, integer register number)
How do you troubleshoot FANUC alarm APSH-121?
Check the MACRO call in the TP program.

Related codes / Codes liés

APSH-119WARN WRITE IO parm %s is wrong typeAPSH-120WARN signal %s does not existAPSH-122WARN GET IO PORT parm %s missingAPSH-123WARN GET IO PORT parm %s is wrong type

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. · Informations indicatives issues du terrain — le manuel du constructeur et ses procédures de sécurité font foi. Ne shuntez jamais un organe de sécurité ; consignez (LOTO) avant toute intervention physique. How this reference is built →