Ford Repair: Coolant temperature gauge indicates low temperature, coolant temp, coolant level

Question
1997 2WD Explorer 4.0 SOHC Auto trans 120,000 miles

Check engine light came on during freeway speed driving - noticed that engine temp gauge was below the dead cold mark.  Heater was pumping hot air when I turned it on.  Pulled off freeway and sat idling for a few minutes and temp gauge started to move up slightly.  OBD II code reader indicated P0125 code.  This description says "Insufficient coolant temperature for closed loop fuel control.

Do you think the problem is with thermostat or the temperature sender, or something else?


Answer
In reference to your comment about the temp sensor NOT being answered---- I would NOT susspect a bad TEMP sensor unless it is indicated by the common routine being followed..you also asked what I thought it was, I answered....check the level and then go for a bad thermostat.
Thanks again,
Erik

Hello and thanks for your question........I'll try to help.
Code po125 is correct------"Insufficient coolant temp for closed loop fuel control".
I would first check your coolant level. If it has dropped, you need to find out where the leak is.
The next thig I would susspect is a bad thermostat. Ford thermostats are known for "going bad".
I hope this help, let me know if I can do more for you,
Erik