Laptop won't boot up correctly

[fgandara]

Sometimes I leave my laptop closed and connected to power for a few days and when I return, the laptop fails to boot up (giving me a black screen of death).  When trying to start the laptop, the fan will run but nothing will display. The power button will still color white but not flash. Sometimes caps lock key will also color white. No other input will force the computer to boot correctly. It will take me like 10ish minutes to actually restart. Once it turns on, it will mention a "CMOS" error. This is not ideal, this has happended a few times. Is there a way mitigate this happening again? 

[Deep_World]

Hi @fgandara,

Welcome to the HP Support Community!

Thanks for reaching out!

We're thrilled to have the opportunity to assist you and provide a solution.

I’m sorry you’re going through this; I understand the concern and don’t worry I’ll help you with this. 

To better understand the issue, could you please provide a few more details?

Does this only happen after the laptop has been left closed and plugged in for a long time, or has it ever happened during normal daily use?

When the CMOS error appears, does it give you a specific message (like “CMOS checksum error” or “CMOS reset”)?

Have you noticed if the system clock/date resets after these incidents?

Here are some troubleshooting steps worth trying:

• Perform a hard reset: Disconnect the charger, hold down the power button for 15–20 seconds, then reconnect and try booting again.
• Update BIOS: Go to HP’s support page for your exact model and install the latest BIOS update. A corrupted or outdated BIOS can cause CMOS errors.
• Check CMOS battery: Even on newer laptops, the small CMOS battery can sometimes be faulty. If it’s weak, the system may lose BIOS settings when left idle. 
• Reset BIOS settings: If you can access BIOS (usually by pressing Esc or F10 at startup), try restoring defaults and saving.
• Run HP diagnostics: Press Esc repeatedly at startup → F2 for diagnostics. Run a full system test to rule out hardware issues.
• Power management settings: In Windows, check advanced power settings to ensure the laptop isn’t entering a deep sleep/hibernate mode that conflicts with BIOS.

 When the laptop finally boots after those 10 minutes, do you notice the system clock/date being wrong, or does it stay correct? That detail will help confirm if the CMOS battery is the issue.

I hope this helps.

I'm glad I could help! 😊 If this resolved your issue, please mark it as "Accepted Solution" and click "Yes" on "Was this reply helpful?" Your feedback not only keeps us going but also helps others find the solution faster! 

Take care and have an amazing day ahead! 

Best regards,

Deep_World

[fgandara]

Hello, 

Apologies for the late reply. It only happens when I come back after leaving the PC plugged in for a considerable amount of time, sometimes hours, sometimes days.

This most recent time, it populated a "CMOS checksum is invalid. CMOS reset (502)" message

I will try what you mentioned the next time this happens. I have not noticed any change in the date or time. 

Is there anything else you might recommend due to the type of error? 

Thanks! 

[Deep_World]

HI @fgandara,

Thanks for your response. 

In addition to the steps previously suggested, we recommend the following:

Update the BIOS
Ensure your system is running the latest BIOS version available for your specific HP model. A BIOS update can resolve checksum-related issues and improve system stability.

Check or Replace the CMOS Battery
If the issue continues, replacing the CMOS (RTC) battery is strongly recommended. A weak battery can intermittently lose stored settings, triggering this error.

Load BIOS Defaults
If the message appears again:

Power on the system and immediately tap F10 to enter BIOS Setup

Select Load Setup Defaults (or “Restore Defaults”)

Save changes and exit 

Regards

Deep_World