Asus X402CA black screen after BIOS changes

[rco3lho]

Hi all, first post here as I'm running out of ideas.
A few days ago Win10 failed to start and any option to get the boot failed. It was on a constant loop attempting Automatic Repair with error “ACPI_BIOS_ERROR” I followed Asus instructions that said to secure boot off and disable CSM to be able to use an USB repair tool.

Enter the BIOS setup menu by pressing and holding F2 key when powering on.
- Switch to "Boot" and set “Launch CSM” to Enabled.
- Switch to "Security" and set "Secure Boot Control" to Disabled.
- Press F10 to save and exit.
- Press and hold ESC key to lunch boot menu when the notebook restarts.

Unfortunately now I have just a black screen. I opened the laptop to remove the CMOS battery and despite being more than 12h out, was not enough to reset. My best bet is to reset the BIOS to be able to access it again but I cannot find a way to clear it to defaults. I need only instruction to re-enter the BIOS. Thank you

 

[Laptop_Nerd]

Hi,

It should have been reset to defaults already when you removed the CMOS battery and put it back in. Here are some more troubleshooting steps that may help.
- Start by doing a hard reboot, remove the battery and unplug the AC adapter then press and hold the power button for 20 seconds then try booting it up again.
- If this will not work, do test the AC adapter if it's working properly. Remove the battery and power the laptop with just the AC adapter connected and see if it will boot up or not. do also try a different AC adapter that has the same voltage and see if it will work or not.
- Proceed with reseating the RAM's if trying a different AC adapter will not work, remove them all for couple of seconds then put them back in making sure everything is seated properly.
- If it will still not work, connect an external monitor and see if you'll get any display from it. If there's a display on the external monitor that could mean that the problem is the built in display.
- But if there's still no display on the external monitor that means the problem lies in the motherboard.

 

[rco3lho]

Thanks for the interest in this thread. I already performed a lot of steps and I cannot get any external video signal. I doubt is an hardware failure as this happened after a BIOS change and many people had the same problem. CSM changes=black screen. This laptop is a particular one as the battery is non removable and the RAM is soldered in the board. I left the board completely disconnected from any cable for 12h without its CMOS battery also. It should have reset the BIOS but I still cannot access it. I didn't discharged any component by using the hard reset method but I don't have many hopes in it. My main hope is that there's a pinout shunt needed to clear the CMOS but Asus doesn't give me the indication on where this can be in the board

 

[rco3lho]

Hi,

It should have been reset to defaults already when you removed the CMOS battery and put it back in. Here are some more troubleshooting steps that may help.
- Start by doing a hard reboot, remove the battery and unplug the AC adapter then press and hold the power button for 20 seconds then try booting it up again.
- If this will not work, do test the AC adapter if it's working properly. Remove the battery and power the laptop with just the AC adapter connected and see if it will boot up or not. do also try a different AC adapter that has the same voltage and see if it will work or not.
- Proceed with reseating the RAM's if trying a different AC adapter will not work, remove them all for couple of seconds then put them back in making sure everything is seated properly.
- If it will still not work, connect an external monitor and see if you'll get any display from it. If there's a display on the external monitor that could mean that the problem is the built in display.
- But if there's still no display on the external monitor that means the problem lies in the motherboard.

As an "Asus Master" would you have access to the schematics of the X402CA Main Board?

 

[rco3lho]

I got it to work! The only way to bring it to life was to flash the BIOS. I had to access a special process only available after you press Ctrl+Fn+Home but as expected, not at the first try. When I was losing hope that this would work, I got the screen that informed me that the BIOS was about to be reset. After the process is completed, the BIOS is set to its default state and the laptop boots normally.