CMOS 502 error message. Cannot get to the BIOS screen to update or restore.

[CareyCC]

HP 17-p121wm - I turn on my laptop and just get a blank screen. I disconnected the CMOS battery and got a CMOS 502 error then blank screen after  Cannot get to BIOS Update screen. Windows key +V or Windows key + B goes no where. BIOS Update with USB drive doesn't work, never can get to BIOS screen. I tried disconnecting my HDD.  I have tried every suggestion in this thread and have not been able to bring my laptop back to life. Have any of you HP employees got any other ideas? HELP PLEASE.

[banhien]

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@CareyCC wrote:

... I disconnected the CMOS battery and got a CMOS 502 error then blank screen after  Cannot get to BIOS Update screen. ...

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@CareyCC 

You need its battery. Please put it back or replace it with a new one.

Regards.

[CareyCC]

I should have included - I left the CMOS battery out for 30 minutes and removed the memory during the same time. I replaced the battery and memory then got the CMOS 502 message when I powered it up the next time.  Any time after that, I did not get any message at all, just a blank screen. The battery measure 3.4 volts so it is good.

Then I proceeded with the other recommendations HP resources and this help forum have suggested. I still get just a blank screen.