Siemens 25001 alarm: Passive encoder hardware fault

Sinumerik detects measurement failure in an encoder or passive ruler. It is an alarm from the Encoder / measurement area, and in the catalog it is listed as “Passive encoder hardware fault”. On the machine you notice it like this: Axis does not reference or loses position, Alarm when moving, Lectura inestable.

On the shop floor it almost always comes from one of these causes: Cable de regla/encoder, Conector sucio, Regla contaminada, Measurement module. Rule out the most likely one on your machine first, before touching parameters or swapping anything.

Do not operate until reliable measurement is recovered. Resetting without fixing the cause first only hides the problem: Siemens 25001 trips again and, in the meantime, you keep working with the machine in bad shape.

With the machine stopped and in a safe state, start with these checks: Identificar eje/encoder, Check accessible connectors with a secure machine, Consult measurement diagnosis. That alone will tell you whether it is the program or whether you need to raise a maintenance job.

With Siemens 25001 active, avoid this: Do not bypass safety devices, Do not manipulate energized electrical cabinet, Do not continue producing if the alarm reappears. Skipping any of these points is what turns a minor stop into an expensive breakdown.

Always if it affects real axis position. If you are not sure how far it goes, stop the machine and report it: a repeat alarm always works out cheaper than a crash.

It is critical: there is a real risk of damage to the machine, the tool or a person. Leave the machine stopped, do not keep resetting it to see if it goes away, and call maintenance before producing again. Guidance reference. Always confirm the full text in the exact machine/control manual.