Well two days ago my 03 mcs with 75k threw a code for coolant temps being too low. Thought maybe air was in the system. Warmed the car up opened the bleeder and didn't seem to have any air come out. My next guess is a thermostat that's stuck open but the coolant temp gauge rises perfectly normal to the middle of the gauge and doesn't fluctuate or anything out of the ordinary. Heater works great, blows hot air once the coolant temp starts to rise too. Is my computer messing with me because its been colder out lately or is it possible I have a stuck open thermostat with no symptoms.

I hate cars. I should've picked an easier, cheaper hobby

 

Unless you have the chrono pack, the temp guage does nothing but show 3 positions...off/cold, running, and "opps, I blew my head-gasket", smoking hot, overheating.
The fact the Gauge shows "middle" only means the motor is warm, and not overheating...the chrono pack option DOES show actual Coolant temp, oil PSI, and temp.
I kinda wonder if you car has a sticky thermosts or may the cooler MINI thermostat made by M7. If you have the m7 one, no worries, but if you have a stick thermostat, they tend to fail pretty quick....mostly closed...so overheat.

 

Not sure why this was stated but non-chrono pack minis have functional temp gauges. Furthermore, this code is nearly always indicative of a stuck or semi-stuck open thermostat rather than a stuck closed thermostat. i would start by replacing the thermostat.

good luck