Siemens Industry Online Support
Siemens AG
Entry type: FAQ Entry ID: 13964195, Entry date: 12/11/2002

BIOS password of PC forgotten

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I forgot the BIOS password of my SIMATIC PC. How can I erase it or set a new one?

In this situation, the only way out is unplugging the power plug and removing the buffer battery on the mainboard for about 15 minutes.

This way, not only the BIOS password will be erased, but also all manual settings (e. g. date and time). After removing the buffer battery, the next time the device is turned on the standard values of the BIOS will be loaded. 

The following EGB and security directives have to be considered indispensably:

  • Before working with electrostatically hazardous blocks (EGB), you have to unload yourself statically.

  • The devices and tools in use must be free of static load.

  • Unplug the power plug before you plug or unplug EG blocks.

  • Touch EG blocks only on the edges.

  • Do not touch connection pins or track conductors on an EG block.

To change the battery, please do the following:

  • Disconnect the PC from the net and unplug all connection cables.

  • Open the device as described in the corresponding manual.

  • Remove the battery from the mainboard. The exact place of the battery can also be found in the manual.

  • After about 15 minutes, put the battery back on the mainboard. Do make sure that the battery is plugged in firmly and correctly.

  • Close the device again.

Now the message "System Configuration Data updated" and an "Error 0251: Default Configuration used" must appear. This indicates that the old settings have been erased and the BIOS default settings have been loaded.

Now you can get into the BIOS again by pressing the "F2 key " and make the necessary settings (e. g. setting time/date, a new BIOS password, boot sequence...).

Security information
In order to protect technical infrastructures, systems, machines and networks against cyber threats, it is necessary to implement – and continuously maintain – a holistic, state-of-the-art IT security concept. Siemens’ products and solutions constitute one element of such a concept. For more information about cyber security, please visit