coolant temperature sender
 

No movement on the temp gauge and the electric fan will run after car is turned off. From reading posts it sounded like the coolant temperature sender. Changed it,and same condition. Getting good heat out of the vents and all else seems normal. Fan will run just for a few minutes after shutting off motor. Thanx-Don

Check what codes are being shown. If it shows a coolant code my guess would be the T-stat. Had a similar problem with the 01. Temp gauge started acting up, changed the temp sending unit hoping that was the problem. Wasn't. Then the A/C quit working. Turned out thr T-stat was stuck open. Engine was'nt reaching proper temp. so computer went into default. Changed the T-stat and that solved both problems.
If this isn't the problem, then it may be in your instrument cluster. Recently went thru that with the 04, but I got lucky on that one.

Thanx- Going to try another sender(you never know) AND the thermostat.