Siemens alarm F31101: Encoder 1: Zero mark failed

What it means

Travel exceeded 1.5 times the parameterized zero-mark distance without a zero mark being detected. The drive therefore lost its reference-pulse stream - typical when the R-track signal is missing entirely, the cable is broken, or the axis moved beyond the expected mark pattern. The fault value counts increments since POWER ON or since the last accepted zero mark.

Likely causes

• reference (R) track absent due to encoder defect or soiled disk
• broken conductor in the encoder cable
• incorrect p0425 spacing setting for the encoder used
• plug contact failure between encoder and Sensor Module

Replacement parts

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

• 6FX2001-… encoder cable

  cable · Common cause

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