Question Getting A2 code after changing the CMOS battery and now PC won't boot ?

[Billy Pilgrim]

Hi
This weekend, I changed my motherboard's CMOS battery.

Since changing the battery the computer won't start at all (not even to BIOS) and the code in the motherboard settles on A2, and that's it.

To try to solve it, I've reseated the RAM, and unplugged and replugged the SATA cables HDD, SSD, DVD drive). I also cursed about it a lot - that didn't help either.

The mobo is an Asus Z-97 Pro. I've had this computer since 2014.

There is some previous history though: the reason I changed the motherboard battery is because a few weeks ago after being shut down (I usually leave my computer on standby), I turned the computer on and it wouldn't start normally at all - it cycled to start again and again (like 20 times... I was thinking "what the hell is this...?") then -magically- it ended up going into Windows and everything was fine. So, over the last few weeks, I've been using the computer almost daily and it worked perfectly fine, but I never shut it down, i'd just put it on standby. Then I shut it down to change the motherboard battery, and here we are..... won't boot.​

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Any tips on how I can fix this?

 

[Phillip Corcoran]

Code A2 means your system cannot find the boot device --- this is not surprising since changing the CMOS battery has caused the BIOS settings to revert to defaults.

You need to access the BIOS settings and set the first boot device to what it should be (ie what it was before you changed the battery).

 

[Billy Pilgrim]

Code A2 means your system cannot find the boot device --- this is not surprising since changing the CMOS battery has caused the BIOS settings to revert to defaults.

You need to access the BIOS settings and set the first boot device to what it should be (ie what it was before you changed the battery).

Thank you very much for your reply.

How can I access the BIOS settings? When it powers up, it doesn't even get as far as the BIOS part of startup.

I'm not sure what the first boot device was. I'm supposing it was the SSD as that is where Windows was installed - does that seem likely to you?

BTW, my computer has an SSD and an HDD.

 

[Phillip Corcoran]

You should be able to access the BIOS settings by pressing <Del> or <F2> as soon as you turn on the PC.

 

[pete_101]

Usually after having had the battery out, you need to load the default settings and go from there. Assuming you have a dedicated graphics card, there is always a possibility it's trying to use the onboard graphics. If you're total stuck, unplug everything you don't need to start with and go from there, so unplug the HDD and remove the graphics card. If you can get it too boot, update the BIOS and then plug in the HDD and graphics card, but do a restart between each...keep each step simple.

 

[Billy Pilgrim]

Thank you all for your replies on this.
I've been way too busy to try these solutions out yet. I'll give them a go as soon as I can.
I checked out info and videos about changing the CMOS battery before doing it and didn't see anything about that resetting everything. Anyway, that's too bad.

 

[BFG-9000]

When the CMOS battery isn't dead yet but I want to change it without messing up the settings, I'll usually change the battery on a running computer so that voltage from the PSU keeps them from getting lost.

As it happens, the Z-97 Pro BIOS also has an option to save those settings into flash memory so you can restore them afterwards. There are 8 slots (under "ASUS OC Profile") so you can check to see if someone has stored a previous configuration in there (it helpfully tells you the dates they were saved too). Otherwise it's going to be trial and error until you find what settings that Windows was installed under (the most obvious to prevent booting being the AHCI setting)

Code A2 is listed as "IDE Detect" issue in the manual. If all of the Intel SATA ports have died, you may still have the two ports attached to an Asmedia controller--but unless you had that controller enabled before with the driver installed, you'd have to reinstall Windows

 

[Billy Pilgrim]

I've followed the advice here and it worked quite easily. I chose the SSD in the BIOS and it loaded up Windows nicely.
That's a huge relief!
Thank you all!