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- HP Community
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- Desktop Operating Systems and Recovery
- CMOS check sum is invalid.

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12-02-2022 01:57 PM
I have a three year old Pavillion desktop computer and in the past few days I am getting a "The CMOS check sum is invalid" during boot up. Like many issues with electronics I thought is was an easy task to get it fixed. But, the Geek Squad people said they could not do it and I had to have HP do it. Others on line described the problem as serious. I read of some solutions which affect the BIOS but there are warning against doing that. So, I can still use the machine by keeping it running or letting the system revert to older BIOS code. Thus, I am not dead in the water but would like to fix the thing. My computer skills are what i would call mediocre but I understand the process by which the BIOS and CMOS act during boot up. Does anyone have any experience with this??
12-07-2022 09:53 PM
@C-130driver
Welcome to the HP support community.
I understand that you are getting CMOS check sum invalid error, I am glad to assist you.
To resolve the CMOS Reset Error (502), restore the BIOS.
- Press enter to restart the PC.
- If the error displays after restarting, try to restore the BIOS using a USB drive. For more information, see the "Recover the BIOS using a USB recovery drive" section of the following:
- For desktop computers, go to HP Desktop PCs - Recovering the BIOS (Basic Input Output System).
- If restoring the BIOS fails, contact HP.
Refer to this HP document for further assistance:- Click here
Keep me posted.
If this helps, please mark the public post as an accepted solution so that it benefits several others.
Cheers.
Sandytechy20
I am an HP Employee
12-07-2022 09:53 PM
@C-130driver
Welcome to the HP support community.
I understand that you are getting a CMOS checksum invalid error, I am glad to assist you.
To resolve the CMOS Reset Error (502), restore the BIOS.
- Press enter to restart the PC.
- If the error displays after restarting, try to restore the BIOS using a USB drive. For more information, see the "Recover the BIOS using a USB recovery drive" section of the following:
- For desktop computers, go to HP Desktop PCs - Recovering the BIOS (Basic Input Output System).
- If restoring the BIOS fails, contact HP.
Refer to this HP document for further assistance:- Click here
Keep me posted.
If this helps, please mark the public post as an accepted solution so that it benefits several others.
Cheers.
Sandytechy20
I am an HP Employee
12-08-2022 07:00 AM
Thanks much for your response. I did solve the problem but in an unexpected way. My original first action was to replace the CMOS battery, without success. I then took the machine to Best Buy where I had bought it. They put one of their own batteries in, again without success and told me the only way was to have HP fix it. That didn't seem to me to be something I would do. They then returned my new battery to the machine and i went home. The next time I booted the machine it came up without any CMOS warning. So, I think their second attempt to install my new battery properly seated it, whereas it was not on previous attempts. I am sticking with that conclusion but will keep your suggestion close at hand in the event the issue returns. Again, thanks for your suggestion. ☺