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Code 20001: [Channel %1: ] Axis %2 no cam signal present

Issue Description & Safety Warning

The Siemens SINUMERIK 840D CNC has triggered a critical [Channel %1: ] Axis %2 no cam signal present 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 Definitions: At the beginning of phase 2 of reference point approac h, the signal from the reduction cam is no longer available. Phase 2 of reference point approach begins when the axis remains stationary after deceleration to the reduction cam. The axis then starts in the opposite dire ction in order to select the next zero marker of the measuring system on leaving the reduction cam or approaching it again (negative/positive edge). Reaction: NC Start disable in this channel. Interface signals are set. Alarm display. NC Stop on alarm. Remedy: Please inform the authorized personnel/service department. Check whether the deceleration path after the approach velocity is greater than the distance to the reference point cam - in which case the axis cannot stop until it is beyond the cam. Use a longer cam or reduce the approach velocity in MD34020 $MA_REFP_VELO_SEARCH_CAM. When the axis has stopped at the cam, it must be checked whether the signal DB31,... DBX12.7 (Deceleration reference point approach) is st ill available at the interface to the NCK. - Hardware: Wire break? Short circuit? - Software: User 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 20001 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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