P0128 After Changing Thermostat

thermostats

#1

So, I had my mechanic change out my thermostat to fix my P0128 code i’ve been getting on my reader as well as the check engine light it causes. Unfortunately after this repair, my check engine light STILL POPPED. I noticed when I checked the Freeze frame, this code popped because my engine temperature was 160 after 7 minutes of driving on the highway! Is it my temperature sensor or is something terribly wrong with my engine? I notice I have a bit of a rough idle at times so I feel it definitely could be the sensor. What do you guys think?


#2

What I found as possible causes:
Low engine coolant level Leaking or stuck open thermostat (likely) Faulty cooling fan (running too much) Faulty coolant temperature (ECT) sensor Faulty intake air temperature (IAT) sensor

Read more at: https://www.obd-codes.com/p0128
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#3

Did your mechanic install the correct thermostat?

To be specific . . . does it open at the correct temperature?

Realistically, I think the temperature should be a little higher than 160 after 7 minutes of freeway driving

If the mechanic didn’t properly bleed air out of the system after the repair, the coolant level could be low, or there could be an air pocket directly at the coolant temperature sensor, both of which will cause the pcm to recognize an incorrect coolant temperature

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#4

Did the mechanic diagnose the issue as a bad thermostat, or did you tell them what to do because your code reader gave a code of P0128?