I've got an issue with the Temp idiot light. About two months ago I started noticing that the Blue indicator for the Water temp seemed to be staying on longer than normal. At least it seemed that way. Now, when I first crank the car up, I get the Red blinking warning. There's no way it's overheating at this point and I've checked the coolant level. All seems O.K. under the hood. After a few minutes, the red indicator goes away and the blue one returns. I suspect that the temperature sensor is going bad. Where is this thing, and can I replace it myself?