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FANUC Alarm MOTN-161 — WARN (… L:…) Can't look ahead

Manufacturer wording — WARN (%s^4 L:%d^5) Can't look ahead
The manual prints placeholders; your controller fills them in with the real group, axis or number.

FANUC MOTN-161 (“WARN (… L:…) Can't look ahead”): Could not get the next motion instruction. First check: Use LOCK PREG instruction to lock position registers.

Updated 2026-09-17 · LogrobotLM reference

Description

Could not get the next motion instruction. This can happen due to: - Using unlocked position registers - Using IF/SELECT statements - Control transfer to another program - Changing the setting for a system variable in the program.

Remedy

Use LOCK PREG instruction to lock position registers. Remove conditional branching (IF/SELECT) if possible. Consolidate programs if possible. Move the parameter instruction to a different line if possible.

Related codes

MOTN-158PM: Original path invalidMOTN-159PM: Joint data error (L:…)MOTN-170Load is close to capacityMOTN-171WARN Overload

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 →