I have a 04 C230 and get a trouble code (don't have it with me) that basically says the the thermostat is opening before the coolant temp is at the correct level (opening too soon). The thermostat is opening at the correct temperature and works correctely after that. I assume the sensor for the coolant on the engine side of the thermostat is bad. Where is it located? Or what else could cause this problem. I have to reset the trouble codes (clear it) and it stays off for a week or so and then is back on again.