What causes FANUC alarm 201?

Part program contains an illegal or malformed command related to the alarm condition. Missing required address word or parameter value in the program block. Programmed value is out of the allowable range. Conflict between active modal codes and the commanded function. Post-processor configuration mismatch for this Fanuc series.

How do I fix FANUC alarm 201?

1. Note the block number shown in the alarm screen and locate that block in the program. 2. Review the command in that block against the Fanuc programming manual. 3. Check for missing words, incorrect values, or conflicting G-code combinations. 4. Verify the program is post-processed for the correct Fanuc series. 5. Correct the program and dry-run at low speed before resuming machining.

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FANUC Controller

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

Alarm 201

Fanuc Alarm 201 - Data Write Error

FANUC 201 alarm indicates a write failure to memory or storage device, commonly caused by memory issues, I/O problems, or corrupted data. This is a hardware/system-level error, not typically a program syntax issue.

FANUCProgram/G-codeIntermediate15-30 minutes

201

Fanuc Alarm 201 - Data Write Error

Write Failure

Root Cause Summary

FANUC 201 alarm indicates a write failure to memory or storage device, commonly caused by memory issues, I/O problems, or corrupted data. This is a hardware/system-level error, not typically a program syntax issue.

Safety

Data not saved

Causes and Fixes

1
Power Down Safely
Follow proper shutdown procedure and lockout/tagout before any hardware inspection.
2
Check Battery Status
Verify battery voltage and condition - low battery can cause write failures.
3
Inspect Memory Cards
Check for loose connections or damaged memory cards/modules.

Service Recommendedmedium confidence

Call a technician if:

·This alarm typically requires technician diagnosis
·If battery replacement doesn't resolve the issue
·If memory hardware replacement is needed

Prevention

Validate programs with simulation before execution
Ensure G-code matches control capabilities

Common Mistakes

Overlooking the specific line number in the alarm
Editing unrelated program sections

Seeing Multiple Alarms?

Seeing another alarm with this one? Enter the code.

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