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Code P0128, Coolant Thermostat?

Tiny
ZANDO
  • MEMBER
  • 2008 FORD ESCAPE HYBRID
  • 2.3L
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 200,000 MILES
Hi all, I just got the following code along with an orange engine light: P0128 Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature).
From what I read, it could be the temperature sensor, and / or thermostat.
I have seen a few YouTube videos on the thermostat change and it is intimidatingly hard to reach (for my level of skill and understanding). But at least I know where that is.
Temperature sensor - I cannot find anything on the www for its location or how to test / change it. Hybrid - that seems to throw everything off.
Help with pictures for the location and suggested steps?
Many thanks in advance
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Saturday, May 11th, 2024 AT 7:29 PM

5 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
Hi,

The code simply indicates the engine is not reaching the correct operating temperature within a specific amount of time. As a result, the vehicle will produce higher emissions.

In most all cases, the thermostat is stuck open and causing this to happen. The repair is usually a new thermostat.

On this vehicle, the thermostat and thermostat housing are one in the same. They are sold as a housing assembly, which includes the thermostat itself.

I attached the directions below. It really isn't a difficult procedure. Take a look at the directions and let me know if you have questions.

Let me know.

Take care,

Joe

See pics below

PS: The cylinder head temperature sensor is located at the top of the engine. See last pic.
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Saturday, May 11th, 2024 AT 9:42 PM
Tiny
ZANDO
  • MEMBER
  • 3 POSTS
Thanks for the visuals!
Should I understand that:
There is only one "stand alone" temperature sensor - and this is the cylinder head temp. Sensor?
- the other element that react to the temperature is the thermostat?
I guess my follow up question is - is there a coolant temperature sensor (separate from the cylinder head sensor) that I should be looking for / consider if it's working properly? Or all is built in the thermostat housing?
Many thanks! Your help is starting to give me confidence that I can tackle to repair myself :)
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Sunday, May 12th, 2024 AT 10:19 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
Hi,

The cylinder head temperature sensor is the one of interest. I feel the thermostat housing with the integral thermostat will eliminate the problem.

As far as the procedure is concerned, it really isn't too hard. If you run into trouble, I will try my best to help.

Let me know.

Joe
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Sunday, May 12th, 2024 AT 6:29 PM
Tiny
ZANDO
  • MEMBER
  • 3 POSTS
Pfuuuu! After much efforts and refresher on some choice words - work completed, and the code is gone. Many thanks to Joe for your response and technical help. Your moral support has been valuable! Thanks again!
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Monday, May 20th, 2024 AT 7:40 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
Hi,

Thanks for the update. I'm glad to know you got it taken care of. Today's cars are becoming extremely sensitive to temperature due to emission regulations.

Regardless, take care of yourself and please feel free to come back anytime in the future.

Take care,

joe
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Tuesday, May 21st, 2024 AT 6:37 PM

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