Temperature sensor flipping out
I have a 2004 330ci with 88k miles on it. Once in a while, usually once every few hours of driving, the temperature alarm goes off repeatedly with readouts of "+50.0", and then "-40.0" I'm pretty sure this is Celcius, although I swear I had the display set to F, since way back when the temp alarm worked correctly, I remember it would beep at 37F. Needless to say, this alarm is happening in very mild weather (60F, cloudy weather) and mild driving conditions.
I assume this is just a broken thermostat somewhere.
Is this a simple enough fix? Or should I just send it over to the dealership?
Thanks for any advice.