P0128 on 2004 Ford FOcus

2004 FORD FOCUS
145,000 MILES • 4 CYL • FWD • AUTOMATIC
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CLRESPOE
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Got P0128 code (Coolant Temp below Thermostat regulating temp) on 2004 Ford Focus ZX3 with 2.3L PZEV Engine. No noticeable change in performance, temperature gauge on dash still functions normally with temperature reading nominal. Where should I start, to figure out the cause of this?
Feb 6, 2011 at 6:36 PM
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CLRESPOE
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I have donated here before, but I can not remember my old login e-mail. I will try to find it and post again if no responses
Feb 6, 2011 at 6:36 PM
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RENAUDTN
  • ✓ASE Certified Mechanic
  • 636 POSTS
  • ASE Certified Mechanic
Hello,

A lot of time, this code indicates a bad thermostat. There are other possible causes for this but thermostat is the likely culprit. Check your thermostat to see if it's stuck open. If it is, replace it, refill with coolant and you should be good to go.
Feb 7, 2011 at 5:35 PM
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