Sinumerik Alarm 20002 Channel %1 axis %2 zero mark not found

Sinumerik Alarm 20002 Channel %1 axis %2 zero mark not found

%1 = Channel number
%2 = Axis name, spindle number

The zero marker of the incremental encoder is not within a defined section. Phase 2 of reference point approach ends when the zero marker of the encoder has been detected after the rising/falling edge of the PLC interface signal “DECELERATION REF- ERENCE POINT APPROACH” (DB 31 – 48, DBX 12.7) has given the trigger start. The maximum distance between the trigger start and the zero marker that follows is defined in the machine data 34060 REFP_MAX_MARKER_DIST. The monitor prevents a zero marker signal from being over traveled and the next being evaluated as reference point signal. (Faulty cam adjustment or excessive delay by the PLC user program).

– NC Start disable in this channel.
– Interface signals are set.
– Alarm display.
– NC Stop on alarm.
– If the axis is a single axis when this alarm is triggered, the alarm is only effective for this axis (not effective for e.g. the channel or mode group)

Please inform the authorized personnel/service department. Check the cam adjustment and make sure that the distance is sufficient between the end of the cam and the zero marker signal that follows. The path must be greater than the axis can cover in the PLC cycle time. Increase the machine data 34060 REFP_MAX_MARKER_DIST, but do not select a value greater than the distance between the 2 zero markers. This might result in the monitor being switched off.

Program Continuation:
Clear alarm with the RESET key. Restart part program


  1. Siemens Diagnostics Guide by Siemens
Sinumerik Alarm 20002 Channel %1 axis %2 zero mark not found