Siemens alarm 20004: [Channel %1: ] Axis %2 reference mark missing

What it means

The connected incremental measuring system does not supply any reference marks at all, so referencing by cam-plus-zero-mark is impossible. This typically appears when the encoder type does not match the configuration or the mark track is dead.

Likely causes

• absolute encoder operated/configured without reference-mark evaluation while REFP_MODE expects marks
• zero-mark track of the encoder defective
• wrong encoder type entered in MD 30240 ENC_TYPE after encoder exchange
• signal evaluation electronics faulty

Replacement parts

We supply the following units for this alarm — tested, warranty-backed:

• 6FX2001 series encoder

  encoder · Common cause

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