CMOS Reset (502) The CMOS checksum is invalid during System reset

[32f0rd]

HP Pavilion 31.5 All-in-One Desktop PC, S/N(edited) , P/N 6Z7T4EA#ABE. Windows 11.

[Kuroi_Kenshi]

Hi @32f0rd,

Welcome to the HP Support Community!

Thanks for reaching out!

Seeing a CMOS Reset (502) error means the data stored on your BIOS chip, which handles the very first steps of starting your computer, has been wiped or corrupted. This usually happens after a sudden power loss, a BIOS update that didn't finalize properly, or because the small coin-shaped battery on your motherboard is dying and can no longer hold the system's "memory" while the PC is turned off.

Perform a Hard Hardware Reset

• Shut down the computer completely and unplug the power cord from the wall.
• Disconnect all external devices like USB drives, printers, and webcams.
• Press and hold the Power button on the case for at least 15 seconds to drain any residual electricity.
• Plug the power cord back in (directly to a wall outlet) and press the Power button to see if it boots normally.

Restore BIOS Defaults

• Restart the computer and immediately tap the F10 key repeatedly (once every second) until the BIOS Setup Utility opens.
• Once inside the BIOS menu, press the F9 key to "Load Setup Defaults."
• Select Yes or OK to confirm you want to restore the factory configurations.
• Press F10 to "Save and Exit" and allow the computer to restart into Windows.

For a detailed guide on handling CMOS and BIOS recovery, refer to the  HP Desktop PCs - BIOS Resetting and Recovery.

Does this error message appear every single time you turn on the computer, or did it only happen once after a power outage?

I hope this helps.

Take care and have an amazing day ahead! 🚀

Best regards,

Kuroi_Kenshi