Code Reader help

[jdlingle]

Mandy's Expedition keeps throwing a code that I have celared twice now. (took me awhile to get around to it on the second one) Code is P0128 Generic- Coolant Thermostat (coolant temp below thermostat regulating temp). Car seems to be running fine, I havent noticed any difference in performance. My questionis does this code mean I need to replace my thermostat? I have never seen a code for low temperature so not really sure why this would be a concern? Still learning this car stuff so any help is appreciated.

[GlennCMC70]

Some cars will have 2 temp sensors. One to run a guage and one to report to the computer. Sounds like the 2nd one is faulty. I assume the temp guage reads normal?
I'm not a Ford guy, so I may be way off base here.

P0128 - Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)
The code P0128 essentially indicates that the specified engine temperature was not achieved in a certain time. Most often this code indicates a bad or stuck open thermostat. Read more about a thermostat here: Thermostat - illustrated glossary.
A bad coolant temperature sensor (ECT), low coolant level or some other problem of the coolant system can also cause the trouble code P0128 to be set. Sometimes, a car manufacturer may recommend an engine computer to be reprogrammed to address this problem.


http://www.obd-codes.com/p0128

A search tells me I'm wrong and a thermostat is likely to issue. Most are made to fail open now days.

[jdlingle]

Thanks! I didnt know about that site. I have bookmarked it for future use now. Whats weird about the code is that it doesnt hit every time the car is ran, just intermittingly. Guess I'll swap out the thermostat and see if that fixes it.

[edrock96GT]

Intermittent= loose connection 99.9% of the time.