Motherboard keeps giving checksum error after installing new battery

motherboard battery cmos

8,579

Solution 1

If you've confirmed the new CMOS battery is outputting the expected voltage, then more than likely it's not your problem.

Next steps:

Reset the BIOS to defaults (option in the BIOS), save and reboot.
If that doesn't work, try (re)flashing the BIOS with the latest version offered by the Motherboard manufacturer (Asus).
If that doesn't help, replace the motherboard.

Solution 2

Even though it may sound obvious, I will add this answer in case someone in the future needs help.

Be sure the new battery is making good contact on both poles. I went thru several rounds of contact cleaning and pin bending/unbending until it finally worked for me. Even if the battery holder seems to keep the battery firm in place, the connectors might need some extra help depending on their age and how the motherboard is oriented (vertically or horizontally) when in use.

Some people try more extreme solutions like soldering an extra wire to bypass whatever is not working well on the motherboard (there are videos about this on YouTube), hopefully you will not need to do this.

8,579

Giorgio

0x2B | ~0x2B

Updated on September 18, 2022

Comments

Giorgio over 1 year
I am repairing a computer with an ASUS M2NBP-VM CSM ACPI motherboard (I am not sure this is the correct description of the motherboard but, at least, this is what gets printed to the screen during boot).

During boot, I get the following error message:
```
CMOS checksum error - Defaults loaded
```
Indeed, the time, date, and boot device priority are reset and the values I had set up before switching the computer off are gone.

My first explanation was that the CMOS battery must be empty so I bought and installed a new one. But the behaviour has not changed: after switching off and disconnecting the power cable, the next time I switch on, the CMOS settings are lost and the error message is printed again.

Any suggestions as to what I should check next?

EDIT

Following the suggestions contained in the answers and comments, I performed a few further tests using another computer that I know is working properly, i.e. it does not lose BIOS settings between reboots.
1. Unplugged computer with its own battery on, waited a minute or two, plugged again, booted: settings are there.
2. Unplugged again, removed battery, put new battery (the one I had used to test the bad computer as described above) in, plugged in, booted, set up time and date, shut down, unplugged, waited for a few minutes, plugged, booted: settings are there. So: the new battery is good.
3. Unplugged again, removed new battery, put old battery from bad computer in, plugged, set up time and date, shut down, unplugged, waited for a few minutes, plugged, booted: settings are NOT THERE. So: the old battery is bad.
So, I have ruled out the case that the new battery is bad. I have performed another test on another computer I am trying to repair. Same model as the bad one above. Removed battery and put the new battery in: it does not retain the settings. The reset jumper is also in the proper position (no reset).

So the problem must be in the main boards. Since I would find it unlikely that they have both broken in the same way, I guess the only test left is to flash the firmware on the main board. Only, I do not understand why this should work: the old firmware has worked before, why should the old firmware have stopped working at some point?
- Ramhound almost 9 years
  
  Can you access the firmware, or is this error preventing that to be possible. My only suggestion would be to flash the firmware.
- marcus almost 5 years
  
  Did the firmware reflash work? I have a board (Intel DG45ID) that exhibits the same problem: does not keep settings even with new batteries. Keeping the old battery used to work (erratically) but now it doesn't anymore.
- Giorgio almost 5 years
  
  @marcus: I did not try it: I had never flashed firmware on a motherboard before and I eventually gave up.
- marcus almost 5 years
  
  @Giorgio Thank you for your reply. My board stopped giving errors after leaving it plugged in for a few hours. I'm not sure it will stay that way but it's something! Looks like the battery recharged itself (??!!) superuser.com/questions/639606/cmos-battery-recharged
Giorgio almost 9 years

"1. Are you setting and saving the settings?": Yes, if I reboot directly without switching the power off, time, date and boot priority are retained: it boots from cd whereas the factory default is boot from hard disk.
rfportilla almost 9 years

I would check the other two things. If it is not that and, as mentioned above, flashing doesn't fix, then it's possible the cmos is bad. This may be trivial based on your needs. If it is bad enough, replace motherboard.
Giorgio almost 9 years

"3. CMOS jumper" According to manualslib.com/download/10121/Asus-M2nbp-Vm-Csm.html, page 31, the jumper is in the correct position (pins 1-2) and should not reset.
Giorgio almost 9 years

"2. Is the new battery good?": It is new (I bought it today). I do not have any tool to measure its voltage but I could try putting it on another motherboard and see if it works there.
rfportilla almost 9 years

If you have another motherboard that is known to be working, why not just pull the battery from that one? It doesn't happen often, but I have had brand new batteries that were bad.
Giorgio almost 9 years

Following your suggestions, I have used the working motherboard to verify the battery.
rfportilla almost 9 years

These are the only things I can think of: the 3 things I mentioned and flashing the bios as Techie007 mentioned. Other than that, I would recommend just living with it or replacing the motherboard. The default settings are usually fine and for most motherboards, it's just an annoying message that pops up when the computer starts. If this is ok, then just deal with it. If not, replace it.