Code 21703: [Channel %1: ] Block %3 axis %2 touch probe not deflected, illegal edge polarity
Issue Description & Safety Warning
The Siemens SINUMERIK 840D CNC has triggered a critical [Channel %1: ] Block %3 axis %2 touch probe not deflected, illegal edge polarity 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 = Axis name, spindle number %3 = Block number Definitions: The selected probe is not (!) deflected and theref ore cannot record any measured value from the deflected to the non-deflected state. Measurement level 2 (MEAWA, MEASA, MEAC) The degree of deflection of the probe at the start of the measurement task is i dentical to the first programmed measurement signal edge. The test is only performed in mode 2. Reaction: Local alarm reaction. NC Start disable in this channel. Interface signals are set. Alarm display. NC Stop on alarm. Remedy: - Check probe - Check start positioning for measuring - Check 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 21703 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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