how to fix CMOS reset 502

[Buntysmum]

Blue screen message   The CMOS Checksum is invalid

[NonSequitur777]

@Buntysmum,

Welcome to our HP Community forum!

The “CMOS Checksum is invalid” error usually indicates a problem with the system’s BIOS settings or CMOS memory, often due to a weak or failing CMOS battery, BIOS corruption, or a reset event.

Try These Steps to Resolve the Issue:

1. Reset BIOS Defaults:

• Turn on or restart the PC and immediately press Esc repeatedly until the Startup Menu appears.

• Press F10 to enter BIOS Setup.

• In BIOS, if available, press F9 to Load Setup Defaults (you may need to confirm).

• Then press F10 to Save and Exit.

This often clears the checksum error if it was caused by misconfigured settings.

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2. Replace the CMOS Battery (CR2032):

• Even though this is an All-in-One PC, it still has a standard CMOS coin-cell battery on the motherboard (usually a CR2032).

• If the battery is weak or dead, the BIOS settings can’t be saved, triggering checksum errors on boot.

• Replacing the battery should resolve the issue long-term.

Note: This requires opening the back panel of the device. If under warranty or if you're uncomfortable doing it yourself, consider having HP service it.

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3. Update the BIOS:

• Go to HP Software & Driver Downloads and search for your model (HP Pavilion 27-xa0000a or use product number 4PC15AV).

• Download and install the latest BIOS version, if available. BIOS updates often include checksum handling improvements and fixes.

 

4. Check for Other Signs of Hardware Issues:

• If the error persists after replacing the battery and resetting the BIOS, there could be a motherboard issue, such as:

  • Corrupt CMOS/NVRAM

  • Failing BIOS chip

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Summary:

• First try a BIOS reset (F9 in BIOS).

• If it returns again, replace the CMOS battery.

• Update BIOS if possible.

• If none of that helps, it may be time to contact HP Support for possible motherboard-level diagnostics.

Kind Regards,

NonSequitur777

[banhien]

@Buntysmum 

Please use

           HP PCs - 500, 501, or 502 errors

Regards.