So I've been driving this S70 for well over a year now with minimal problems. My new job means that I'm driving much less than normal however I still check fluids and tires..nothing out the ordinary.

It's just starting to get cold around here and I left to go visit some friends. I thought it was a bit odd that the temp gauge was going up much slower than usual and I wasn't getting much in the way of heat out of the heater. About ten miles down the road (after doing +45 mph) the check engine light came on and the temp gauge still wasn't up to normal operating temp.

The next day coming home, the temp gauge was bottomed out for the first ten miles and then fairly quickly rose to operating temp. Still have the check engine light on and when I pulled into the garage, the radiator fan was running full speed even after I turned the car off.

I don't have an OBDII reader, but I'm willing to bet I've got a sticky/shot thermostat?

Thanks for any input...