Yeah it could be the thermal sensor chip under the heat sink is defective. That's not a user serviceable part.
PrecisionX is written for Nvidia chips by Nvidia. It will tell you load and temps along with other aspects of the card. EVGA - Software - EVGA PrecisionX 16
You'll have to create an account to get it though. It's painless. I use PX when I want a peek at the card to make sure the temps are fairly stable. It's a lot better than 3rd party tweak and monitor software.
BTW Do you have Bionc or folding at home or something like that that uses the GPU? If you do does it start up with windows? If that's the case disable it starting up at boot up or set it to manual. That way it only starts up when called for.