What causes Siemens SINUMERIK alarm 402602?

Invalid channel number passed to FC26 in the PLC program. FC26 called with a parameter that exceeds the valid range for this SINUMERIK configuration. PLC program version mismatch — FC26 call parameters not updated after a machine configuration change. Number of configured channels in SINUMERIK does not match the FC26 parameter. PLC program downloaded with incorrect machine data for this specific machine tool.

How do I fix Siemens SINUMERIK alarm 402602?

1. Check the SINUMERIK PLC alarm details for the specific parameter value that caused the error. 2. Review the PLC program — find the call to FC26 and verify the parameter values are within valid range. 3. Compare the FC26 parameter against the actual number of configured channels in the SINUMERIK machine data. 4. If the PLC program was recently modified or the machine configuration changed, verify FC26 calls were updated accordingly. 5. Contact the machine tool builder if the PLC program source is not available for review.

Siemens SINUMERIK codes

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Siemens SINUMERIK Controller

Program/G-code · Intermediate · 30-120 minutes

Alarm 402602

Siemens 840D 402602 - Parameter ChanNo impermissible in FC26

This alarm occurs when a mode group or channel number parameterized in FC26 does not exist. Correct the parameter or program to reference a valid channel.

Siemens SINUMERIKProgram/G-codeIntermediate30-120 minutes

402602

Siemens 840D 402602 - Parameter ChanNo impermissible in FC26

Parameter ChanNo impermissible in FC26

Siemens SINUMERIK alarm 402602: Parameter ChanNo impermissible in FC26. An impermissible or invalid parameter was passed to PLC function block FC26. This indicates a PLC programming error or configuration mismatch in the machine tool builder ladder program.

Root Cause Summary

This alarm occurs when a mode group or channel number parameterized in FC26 does not exist. Correct the parameter or program to reference a valid channel.

Safety

Refer to Siemens documentation
Ensure qualified technician performs repairs

Causes and Fixes

1
SAFETY FIRST - Stop all operations
Ensure machine is in a safe state, all axes are stopped, and emergency stop is accessible before proceeding with diagnostics.
2
Locate the error
Check the alarm message for the specific block or line number triggering the error.
3
Verify parameter
Ensure the mode group or channel number in FC26 is valid and exists in the system configuration.
4
Correct and test
Update the parameter, clear the alarm, and restart the program in safe mode or simulation first.

Service Recommendedmedium confidence

Call a technician if:

·If you are not trained in Siemens control system programming
·If the alarm persists after verifying parameters and configuration
·If access to system configuration settings is restricted
·If you are unsure about any step in the diagnostic process

Prevention

Validate mode group and channel numbers before running the program
Use simulation to catch parameter errors early
Maintain proper documentation of system configuration
Implement change control procedures for program modifications

Common Mistakes

Using parameters from a different machine or control version
Overlooking the specific block referenced in the alarm

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