What causes FANUC alarm 255?

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 255?

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 255. 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 255

Fanuc 255 - Illegal tool life command

FANUC 255 alarm occurs when the control detects an improperly formatted or invalid tool life management command in the part program. This typically involves G10 L3 commands used for tool life registration, illegal parameter values, or attempts to register tool life data for non-existent tool groups or tools that exceed system limits.

FANUCProgram/G-codeIntermediate5-30 minutes

255

Fanuc 255 - Illegal tool life command

ILLEGAL TOOL LIFE COMMAND

Root Cause Summary

FANUC 255 alarm occurs when the control detects an improperly formatted or invalid tool life management command in the part program. This typically involves G10 L3 commands used for tool life registration, illegal parameter values, or attempts to register tool life data for non-existent tool groups or tools that exceed system limits.

Safety

Verify corrected program or parameters before resuming machining

Causes and Fixes

1
Locate the line number where the alarm occurred and review the G10 L3 command format. Correct format is: G10 L3 P_ Q_ (tool group and number) with L_ (life value) and/or H_ (life type).
2
Verify P (tool group number) is within valid range (typically 1-128 or 1-256 depending on system). Check Q (tool number within group) does not exceed maximum tools per group defined in parameters.
3
Confirm H address value is valid: H1=count-based, H2=time-based (minutes). Ensure L address contains positive integer values appropriate for the life type selected.
4
Check that tool life management is enabled in parameter 6800#0 (TLM) and parameter 6813 (number of tool groups) is set correctly. Tool group must be registered before individual tools can be added.
Modifying parameters requires proper authorization and machine restart.

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