Code 18203: [Channel %1: ] Block %2 curve table: instru ction CTABDEF not within CTABDEF
Issue Description & Safety Warning
The Siemens SINUMERIK 840D CNC has triggered a critical [Channel %1: ] Block %2 curve table: instru ction CTABDEF not within CTABDEF alarm. Immediate attention from a qualified operator or maintenance technician is required to prevent secondary damage to the equipment or spoiled parts during the manufacturing cycle. Always ensure standard safety and LOTO procedures are followed before accessing electrical cabinets.
Official Troubleshooting Steps
Parameters: %1 = Channel number %2 = Block number, label Definitions: In the program, the instruction CTABDEF that star ts the definition of curve tables, is programmed within the definition part of a curve table. This is not allowed, as the current curve table must be completed with CTABEND first. Reaction: Interpreter stop NC Start disable in this channel. Interface signals are set. Alarm display. Remedy: Remove command CTABEND from program or insert instruction CTABDEF (..) in the relevant program position. Instructions CT ABDEF and CTABEND must be programmed in the same program level (main program or subroutine). Restart the program. Program Continuation: Clear alarm with the RESET key. Restart part program
Source: SINUMERIK 840D sl / 840Di sl / SINAMICS S120 Diagnostics Manual (DAsl, 03/2009)
Last reviewed: 2026-07-01 · Verified against the manufacturer’s official documentation.
About Siemens SINUMERIK 840D CNC Alarms
Siemens controllers include extensive self-diagnostics that flag or halt the machine when a fault is detected. Error code 18203 on the SINUMERIK 840D CNC identifies one specific fault condition — its documented cause and the official corrective steps are listed above, sourced from Siemens's service documentation. Always confirm against the manual for your exact machine configuration and follow LOTO procedures before servicing.
Complete Alarm List: 4014 Siemens SINUMERIK 840D CNC codes.
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