For a step-by-step visual on resetting a forgotten password by overwriting the program via an MMC card, check out this tutorial:
offer software specifically designed to read passwords from S7-300 MMCs. 2. The "Nuclear Option": Factory Reset unlock s7300 plc password work
Siemens SIMATIC S7-300 PLC passwords can be removed by performing a Memory Reset (MRES) via the mode selector switch to clear the CPU memory and password. Alternatively, authorized users can manage or remove protection levels and "Know-How" block protection directly through the Hardware Configuration in SIMATIC Manager. For lost passwords on critical systems without backups, contacting a Siemens service partner for professional support is recommended. For a step-by-step visual on resetting a forgotten