Siemens SINUMERIK codes
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Siemens SINUMERIK Controller

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

Alarm 402502

Siemens 840D 402502 - Parameter ChanNo impermissible in FC25.

Siemens SINUMERIK alarm 402502: Parameter ChanNo impermissible in FC25. An impermissible or invalid parameter was passed to PLC function block FC25. This indicates a PLC programming error or configuration mismatch in the machine tool builder ladder program.

Siemens SINUMERIKProgram/G-codeIntermediate30-120 minutes

402502

Siemens 840D 402502 - Parameter ChanNo impermissible in FC25.

Parameter ChanNo impermissible in FC25.

Siemens SINUMERIK alarm 402502: Parameter ChanNo impermissible in FC25. An impermissible or invalid parameter was passed to PLC function block FC25. This indicates a PLC programming error or configuration mismatch in the machine tool builder ladder program.

Safety

  • Refer to Siemens documentation
  • Ensure qualified technician performs repairs

Common Causes

  • Invalid channel number passed to FC25 in the PLC program
  • FC25 called with a parameter that exceeds the valid range for this SINUMERIK configuration
  • PLC program version mismatch — FC25 call parameters not updated after a machine configuration change
  • Number of configured channels in SINUMERIK does not match the FC25 parameter
  • PLC program downloaded with incorrect machine data for this specific machine tool

Troubleshooting Steps

  1. 1Check the SINUMERIK PLC alarm details for the specific parameter value that caused the error.
  2. 2Review the PLC program — find the call to FC25 and verify the parameter values are within valid range.
  3. 3Compare the FC25 parameter against the actual number of configured channels in the SINUMERIK machine data.
  4. 4If the PLC program was recently modified or the machine configuration changed, verify FC25 calls were updated accordingly.
  5. 5Contact the machine tool builder if the PLC program source is not available for review.

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