Cadillac Repair: Outside temperature, diode, thermometer

Question
I have a 2000 Deville. About a month ago, i started noticing that the thermometer for the outside temp was off. It was reading about 20 degrees higher than it actually is. Its just got worse from there. Im in Ohio, it was like 45 degrees F yeaterday, my display read 140 degrees. Im thinking its probably something simple, but im stuck, I cant find the thermometer itself to see if its being blocked by something or covered with something. What should I do from here?

Answer
Lift your hood up, somewhere in front of the radiator, most likely towards the top left side, there is a small box with a diode in it. http://info.rockauto.com/SMP/SMPDetail3.html?AX27.html this is an image of one. But there is most likely a short or the sensor is just faulty and needs to be replaced.