Siemens alarm 25001: Axis %1 hardware fault of passive encoder

What it means

The second (passive) measuring system of the axis reports a hardware fault, i.e. its signals are interrupted, implausible or absent. The passive encoder normally serves as monitoring/back-up system, so its failure degrades redundancy even if the axis still moves on the active encoder.

Likely causes

• direct measuring system (linear scale) defective or heavily contaminated
• broken encoder cable, loose connector or damaged coupling
• screening/earth bond interrupted causing signal corruption
• evaluation electronics in the drive measuring circuit faulty

Replacement parts

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

• linear/direct measuring system (per machine spec)

  encoder · Common cause

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• 6FX5002 series encoder signal cable

  cable · Common cause

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