What causes FANUC alarm 1099?

Incorrect syntax in a variable name or expression. Attempting to use a variable that requires a suffix (e.g. array index) without providing one. Trying to access an array element with an index value that is out of the valid range.

How do I fix FANUC alarm 1099?

1. Carefully review the program code where this alarm occurred and check for any variable names that are missing a required suffix, such as an array index. 2. Verify that any array accesses are using a valid index value that is within the defined size of the array. 3. If the issue is in a custom macro, double-check the syntax and structure of the macro code to ensure it is properly formatted. 4. Try running the program in single-block mode to identify the specific line of code triggering the alarm. 5. If the issue persists, consult the Fanuc documentation or reach out to the control manufacturer for further guidance.

axismd.ai

FANUC Controller

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

Alarm 1099

Fanuc Alarm 1099 - ILLEGAL SUFFIX

Alarm 1099 ILLEGAL SUFFIX occurs when macro variable programming contains syntax errors related to variable addressing. This includes missing suffixes on system variables that require them (like #_TCXX or #_DRVXX), or when the index value within brackets exceeds the valid range for that variable type. The alarm is generated during program execution or verification when the macro compiler encounters improperly formatted variable names.

FANUCProgram/G-codeIntermediate15-30 minutes

1099

Fanuc Alarm 1099 - ILLEGAL SUFFIX

MACRO ALARM 1099

Root Cause Summary

Alarm 1099 ILLEGAL SUFFIX occurs when macro variable programming contains syntax errors related to variable addressing. This includes missing suffixes on system variables that require them (like #_TCXX or #_DRVXX), or when the index value within brackets exceeds the valid range for that variable type. The alarm is generated during program execution or verification when the macro compiler encounters improperly formatted variable names.

Causes and Fixes

1
Press EDIT or MEM mode, navigate to the program causing the alarm and identify the line number shown in the alarm detail. Search for system variables with underscore prefix (#_) in that area.
2
Check all system variable references against valid ranges: #_TC[1-200] for tool compensation, #_DRV[n] where n=controlled axis number (1-8 typically), #_OPM[1-8] for operator messages. Verify the Fanuc system documentation for your specific control series (0i/16i/18i/30i/31i/32i) as ranges vary.
3
Correct the variable syntax ensuring proper suffix format. Example: change #_TC to #_TC[5], or reduce #_DRV[12] to valid axis count. For indirect addressing like #_TC[#100], verify #100 contains a value within valid range.
4
Execute program in single block mode (SINGLE BLOCK button ON) or use PROGRAM CHECK function (SETTING screen parameter 3100#0=1 enables background edit) to verify correction before running.

DIY Feasiblehigh confidence

Call a technician if:

·Parameter corruption suspected
·Macro variable memory allocation issues
·Repeated alarms after syntax corrections

Prevention

Use program syntax checker before running new programs
Maintain consistent variable naming conventions
Document custom macro variable ranges
Regular backup of working programs

Common Mistakes

Forgetting brackets on system variables
Using tool numbers that don't exist in tool table
Exceeding macro variable memory limits
Mixing variable types without proper syntax

Related Alarms

1098 1100 1101 1102

Seeing Multiple Alarms?

Seeing another alarm with this one? Enter the code.

Get machine-aware diagnosis

AxisMD logs alarms against your actual machines, tracks patterns, and gives AI context your manual doesn't have.

Start free

Was this guide helpful?

Always verify with your machine manual or a certified technician before performing service procedures.