CPU Fan error on first startup - Sabertooth Z77, Core i7 3770k, Hyper 212 EVO

[Bat Svetlio]

Hello, everyone. As briefly described in the title, I have a CPU fan error on startup.
This first occurred a couple of days ago, my PC was switched off for over a week (I was traveling), I switch it on, this error pops up.
When I first installed the EVO a while ago, I had similar problems. Quick lookups around here & I disabled the CPU Fan Speed check on startup in BIOS - everything ran smoothly.
This leads me to the conclusion that my CMOS Battery is dead (been having this mobo since August 2012) BUT a lot of my search results explained inconsistencies with the Clock (01.01.2009, etc.). This is not the case with me, the clock is fine, only the fan setting (and other settings I have made in BIOS) have reset to default.
So my questions are:
1) How can I be absolutely certain that my CMOS is the problem (I want to be completely sure before I start disassembling the EVO & Thermal Armor)?
2) If the issue is not with the CMOS, what should I do next to further troubleshoot this?
I am happy to provide additional info, if required.

 

[QwerkyPengwen]

The CMOS shouldn't be dead but it could be faulty. You shouldn't have to disassemble everything to get to it. There should be jumpers on the board you can access for resetting the CMOS, try doing a jumper reset and seeing if the setting changes will stick. If they don't (and you can access the battery without taking everything apart) try taking the battery out and leaving it alone for about 15-20min and then putting it back in and seeing if the setting changes in your bios will stick. If this doesn't work then you might need a new battery.

 

[Bat Svetlio]

I tried resetting the CMOS by moving the jumper to pins 2 & 3 for 5-10 seconds, as I read in another topic. However the settings didn't reset. How long do you suggest to keep the jumper on? Tonight I'm trying with ~30.
Also, if it still doesn't work, I'll just buy a new battery and tear apart the whole thing, since it's about time I cleaned my rig, so it will be disassembled either way.

 

[Bat Svetlio]

Held the reset switch about 30-40 seconds, did the job. Also, changed the battery & cleaned the whole rig. Everything works smooth now. Thanks for the help!