Siemens S7-1500 CPUs use a project-level security model stored in the PLC and TIA Portal project. There are three common scenarios:

2. The Primary Solution: Resetting via the SIMATIC Memory Card (SMC)

If you can still establish an online connection (e.g., if you have "Read access" but lost the "Write access" password), you can use TIA Portal to perform a factory reset.

This is the most common method if you cannot go online due to the forgotten password. By clearing the SIMATIC Memory Card , you force the PLC to start with an empty configuration. Power off the CPU and remove the SMC. Step 2: Insert the card into a standard PC card reader.

If you contact Siemens support, they will guide you through the physical "Reset password" process or request that you send the CPU to a certified service center with proof of purchase.