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Discussion Starter · #1 ·
I have 2015 Fusion with 2.5 engine. I have a p0128 code. I was wanting to know if this engine has two temperature sensors, or one. I see a "cylinder head temperature sensor", but can't locate a "coolant temperature sensor". If it does have the coolant temp sensor, where is it? Vin # is3FA6POG75FR181488. Thanks, GaryK
 

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Phoenix, AZ 85008
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Welcome to the FFO!

With the code you have determined the sensor is bad? Because there are a couple of other issues that can cause that code to be present.
A bad or missing thermostat.
Bad wiring or connector(s)

And yes, there are more than one engine temp sensor. Just one engine coolant temp (ECT) sensor which is located on drivers side of the engine under the air intake hose on a small black plastic pipe that has a small hose. The OE sensor has a brass base with a white connector end.

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Thanks. No, i don't know if it's thermostat or sensors or wiring. I replaced thermostat about 25K miles ago. The engine has 103K on it. I wanted to do some tests on the sensors. I can drive from a cold start and temp stays at 160 for several miles. Came back home and let the car idle and it goes up to 198 and eventually 205.
 

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I understand that you can unplug the coolant sensor and the temp reading should go to -40 and if you short the two wires, it should go to 250 degrees. Is this indeed a good test on this car?
 

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Based on the shop manual, the stock thermostat is designed to start opening around 185 f degrees.
Not fully open until 207 f degrees

As far as testing the ECT sensor I do not know the values. The shop manual did not show much for the ECT sensor.
I have not looked it up, my guess is the ECT sensor sign goes to the PCM and the PCM operates any dash gauge if there is one.
My daughter has a 2010 Fusion. She is out and about otherwise I might look at her ride.

Guessing ' based on the code and you replaced the thermostat, and the coolant temps you are posting are rather low, I think you have a thermostat that is open or more open than desired. OR there is air in the system.

Did you have the code before you replaced the thermostat?

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The cooling system is designed to heat up as fast as possible. When that happens the air fuel mixture burns more completely.

Which the cooling system can get to 240f or 250f without harm, the desired temp is 205f to 215f. Below that temp the engine is not running as efficiently as it could.

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Discussion Starter · #7 ·
No, i didn''t have this code before i changed the thermostate, and it's been a couple years ago that i did that. The reason i changed the thermostate is beceause there was a leak at the housing. It was aftermarket from Rock Auto. I'v looked online at many sites and none show a coolant temp sensor for my 2.5 gas engine. The only sensor anyone shows is the cylinder temp sensor that is one top of the engine. That's why i asked if there were 2 sensors.
 

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