What causes FANUC alarm 238?

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 238?

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 238. 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 238

Fanuc 238 - Gentle start data error

Alarm 238 GENTLE START DATA ERROR occurs when the gentle start/stop function parameters in the part program are incorrectly specified or out of acceptable range. This alarm is typically triggered by invalid G05.1 command syntax, improper acceleration values, or incompatible gentle start parameters that the control cannot process.

FANUCProgram/G-codeIntermediate5-30 minutes

238

Fanuc 238 - Gentle start data error

GENTLE START DATA ERROR

Root Cause Summary

Alarm 238 GENTLE START DATA ERROR occurs when the gentle start/stop function parameters in the part program are incorrectly specified or out of acceptable range. This alarm is typically triggered by invalid G05.1 command syntax, improper acceleration values, or incompatible gentle start parameters that the control cannot process.

Safety

Verify corrected program or parameters before resuming machining

Causes and Fixes

1
Identify the program block number shown with the alarm and locate the G05.1 command in your part program.
2
Verify the Q value is within the valid range (typically Q1-Q3 for gentle start levels). Check parameter manual for your specific control version.
3
Ensure G05.1 Q0 is used to cancel gentle start mode before program end or mode changes.
4
Correct the G05.1 syntax to match format: G05.1 Q[1-3] (activation) or G05.1 Q0 (cancellation), then reset alarm and restart program.

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