FANUC Alarm APSH-121 — WARN can't write signal …
Manufacturer wording — WARN can't write signal %s
The manual prints placeholders; your controller fills them in with the real group, axis or number.
FANUC APSH-121 (“WARN can't write signal …”): The WRITE IO MACRO was called but the signal could not be found. First check: Check the MACRO call in the TP program.
Updated 2026-09-17 · 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
Check the MACRO call in the TP program.
Related codes
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 →