What causes FANUC alarm 155?

The T code specified in the same block as M06 does not match the tool group currently active in the tool management system. Tool group numbers are incorrectly assigned in the tool offset table, causing a mismatch when M06 is executed. The machining program was written for a different machine configuration where tool grouping is set up differently. Tool life management is active and the programmed T code belongs to a different group than what the control expects for the current operation. A typo or incorrect T code number was entered in the block containing M06, referencing the wrong tool group.

How do I fix FANUC alarm 155?

1. Check the tool offset page on the control and verify that the T code programmed in the M06 block belongs to the correct tool group currently in use. The group number must match what the control has registered. 2. Review the specific block in the program that triggered the alarm and confirm the T code number is correct and intentional. Compare it against your setup sheet or tool list. 3. If tool life management is enabled, go to the tool life management screen and verify the group assignments for all tools. Make sure the T code in question is assigned to the expected group. 4. Correct the T code in the program to match the proper tool group, or reassign the tool to the correct group in the tool management table if the program is correct. 5. After making corrections, reset the alarm, perform a dry run or single-block execution through the affected section to confirm the alarm does not return before running the full program.

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FANUC Controller

Program/G-code · Intermediate · 15-30 minutes

Alarm 155

Fanuc Alarm 155 - ILLEGAL T-CODE COMMAND

Fanuc Alarm 155 occurs when the T-code specified in the same block as M06 (tool change command) does not match the tool magazine group currently selected or does not exist in the active tool management configuration. This is typically caused by programming errors where the requested tool number is outside the valid range, attempting to call a tool from an inactive magazine group, or parameter mismatches between the tool magazine configuration and the program.

FANUCProgram/G-codeIntermediate15-30 minutes

155

Fanuc Alarm 155 - ILLEGAL T-CODE COMMAND

PROGRAM ALARM 155

Root Cause Summary

Fanuc Alarm 155 occurs when the T-code specified in the same block as M06 (tool change command) does not match the tool magazine group currently selected or does not exist in the active tool management configuration. This is typically caused by programming errors where the requested tool number is outside the valid range, attempting to call a tool from an inactive magazine group, or parameter mismatches between the tool magazine configuration and the program.

Causes and Fixes

1
Check the program block that triggered the alarm and note the T-code value specified with M06 (e.g., T0135 M06).
2
Navigate to SYSTEM > PARAM and check parameter 5911 (maximum tool number) and parameter 5912 (number of tool pots). Verify the T-code in the program does not exceed these values.
3
If using multiple magazine groups, check parameters 5913-5916 for group definitions and verify parameter 5910 (magazine group selection) matches the intended group for the requested tool.
4
Correct the program to use a valid T-code within the defined magazine range, or adjust magazine parameters if physical configuration supports additional tools.
Changing magazine parameters requires understanding of the physical ATC configuration. Incorrect settings may cause ATC mechanical errors or crashes.

DIY Feasiblehigh confidence

Call a technician if:

·Tool changer mechanical issues
·Parameter corruption requiring backup restoration
·Custom macro debugging beyond operator skill level

Prevention

Always verify T-code ranges before programming
Maintain consistent tool numbering system
Regular tool life management table maintenance
Document custom macro modifications

Common Mistakes

Using T-codes outside parameter-defined range
Forgetting tool group selection before M06
Not registering new tools in tool life management
Mixing different T-code numbering conventions

Related Alarms

156 157 158 401 402

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