Siemens 2000/20000 alarm: PLC sign-of-life / PLC not started

Sinumerik does not receive correct life signal from the PLC or the PLC has not started. It is an alarm from the PLC/machine area, and in the catalog it is listed as “PLC sign-of-life / PLC not started”. On the machine you notice it like this: The machine is not ready, PLC alarms at start-up, HMI/NC waits for machine signals.

On the shop floor it almost always comes from one of these causes: PLC detenido, PLC program or communication, I/O module, Incomplete start after electrical failure. Rule out the most likely one on your machine first, before touching parameters or swapping anything.

Reset solo tras recuperar estado PLC listo. Resetting without fixing the cause first only hides the problem: Siemens 2000/20000 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: Anotar alarmas NC/PLC completas, Review PLC diagnosis, Reboot following OEM procedure. That alone will tell you whether it is the program or whether you need to raise a maintenance job.

With Siemens 2000/20000 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.

If PLC does not start or there are module/I/O messages. 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.