What causes FANUC alarm 156?

Machine system or function indicated by the alarm name has detected a fault. Control parameter or configuration error related to the alarm condition. Hardware component fault on the CNC or machine. Part program error or illegal operation for the indicated function. Machine interlock or safety condition not satisfied.

How do I fix FANUC alarm 156?

1. Note the alarm number and check the Fanuc alarm screen for any sub-code or additional details. 2. Identify the specific machine system or function from the alarm name. 3. Power cycle the machine to clear transient faults. 4. Consult the Fanuc parameter or operator manual for alarm 156 specific remedy. 5. Contact Fanuc service if the alarm persists after basic troubleshooting.

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FANUC Controller

Program/G-code · Basic · 10-20 minutes

Alarm 156

Fanuc Alarm 156 - P/L COMMAND NOT FOUND

Alarm 156 P/L COMMAND NOT FOUND occurs when the CNC system expects a tool group number (P) and tool number (L) specification at the beginning of a machining program, typically when using tool group management or tool life management functions. This alarm is triggered when the control is configured for tool group programming (Parameter settings enable this feature) but the NC program lacks the required P and L address codes in the correct sequence.

FANUCProgram/G-codeBasic10-20 minutes

156

Fanuc Alarm 156 - P/L COMMAND NOT FOUND

SYSTEM ALARM 156

Root Cause Summary

Alarm 156 P/L COMMAND NOT FOUND occurs when the CNC system expects a tool group number (P) and tool number (L) specification at the beginning of a machining program, typically when using tool group management or tool life management functions. This alarm is triggered when the control is configured for tool group programming (Parameter settings enable this feature) but the NC program lacks the required P and L address codes in the correct sequence.

Causes and Fixes

1
Review the NC program structure. When tool life management is enabled, the program must begin with P___ (tool group number) and L___ (tool number within group) before any T code or tool change command.
2
Check the program format. Correct format should be: O0001; P01 L01; (other program code). Ensure P and L are on the same block or consecutive blocks depending on parameter settings.
3
Navigate to SYSTEM > PARAM and verify parameter 6800#0 (TGL - Tool Group Management) and parameter 6813 (Tool Life Management settings). If these are enabled, P/L commands are mandatory.
4
Edit the NC program to include the P and L addresses at the program beginning, or temporarily disable tool life management in parameters if not required for this operation.
Disabling tool life management will affect all programs and tool tracking. Consult machine tool builder documentation before changing parameter 6800#0.

DIY Feasiblehigh confidence

Call a technician if:

·Parameter changes don't resolve alarm after restart
·Multiple programs affected simultaneously
·Alarm persists after syntax corrections

Prevention

Always include P/L commands in subprogram headers
Use consistent program numbering standards
Regularly backup and verify program syntax
Document parameter settings for tool group management

Common Mistakes

Forgetting P/L commands when converting from other CNC formats
Using incorrect parameter 3201-3210 settings
Mixing up P and L command positions in program header
Not restarting control after parameter changes

Related Alarms

155 157 078 079

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