What causes FANUC alarm 209?

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 209?

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 209. 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 209

Fanuc 209 - Illegal synchronous control command

Alarm 209 occurs when the CNC control encounters an improperly formatted synchronous control command or a command combination that violates the control's execution rules. This typically involves G00.3, G00.4, G05.2, or synchronized motion commands with incorrect syntax, missing parameters, or incompatible mode settings.

FANUCProgram/G-codeIntermediate5-30 minutes

209

Fanuc 209 - Illegal synchronous control command

ILLEGAL SYNCHRONOUS CONTROL COMMAND

Root Cause Summary

Alarm 209 occurs when the CNC control encounters an improperly formatted synchronous control command or a command combination that violates the control's execution rules. This typically involves G00.3, G00.4, G05.2, or synchronized motion commands with incorrect syntax, missing parameters, or incompatible mode settings.

Safety

Verify corrected program or parameters before resuming machining

Causes and Fixes

1
Review the program line number displayed with the alarm. Check for G00.3, G00.4, G05.2, or other synchronous control commands.
2
Verify all required parameters are present for the synchronous command. Consult the Fanuc parameter manual for your specific control series (0i, 30i, 31i, etc.) to confirm proper syntax.
3
Check that axis designations are valid for your machine configuration and that no undefined or disabled axes are being commanded.
4
Validate parameter values are within acceptable ranges. Check parameters 8133-8145 (synchronous control parameters) to ensure they match your program requirements.

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