What causes FANUC alarm 161?

Part program contains an illegal G-code or M-code combination for this alarm type. Missing or incorrect address word in the program block. Axis or parameter value out of range for the commanded function. Required option not enabled on this CNC for the commanded function. Conflict between active modal states and the commanded function.

How do I fix FANUC alarm 161?

1. Note the block number shown on the alarm screen and locate that block in the program. 2. Review the command in that block against the Fanuc programming manual for alarm 161. 3. Check for missing address words, incorrect values, or conflicting G-code combinations. 4. Verify any required CNC options are enabled if using advanced functions. 5. Correct the program and verify the fix before restarting machining.

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FANUC Controller

Program/G-code · Intermediate · 5-30 minutes

Alarm 161

Fanuc 161 - Illegal command in constant cutting

Alarm 161 occurs when an incompatible G-code command is programmed while constant surface speed (G96) or constant pitch threading mode is active. The control cannot execute certain commands like canned cycles, tool nose radius compensation, or specific positioning moves while these constant control modes are engaged.

FANUCProgram/G-codeIntermediate5-30 minutes

161

Fanuc 161 - Illegal command in constant cutting

ILLEGAL COMMAND IN CONSTANT CUTTING

Root Cause Summary

Alarm 161 occurs when an incompatible G-code command is programmed while constant surface speed (G96) or constant pitch threading mode is active. The control cannot execute certain commands like canned cycles, tool nose radius compensation, or specific positioning moves while these constant control modes are engaged.

Safety

Verify corrected program or parameters before resuming machining

Causes and Fixes

1
Locate the N-block number in the alarm message and examine the program line where the alarm occurred.
2
Check if G96 (constant surface speed) is active in the current program modal state before the alarm line.
3
Identify if the alarm line contains G70-G76 canned cycles, G41/G42 compensation, or other restricted commands.
4
Insert G97 (constant spindle speed mode) before the incompatible command, then reactivate G96 after the operation if needed.
Ensure appropriate spindle speed is specified with G97 to prevent spindle overspeed or stalling.

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