I'm new to this forum, this will be my first post. Looking for advice. I replaced my valve cover and when I did that I also put in a new cylinder head temp sensor. Finished the job and after 30 miles my check engine popped on. So I scanned it and it threw the code P0128. My coolant temp is apparently below the proper temp but my scanner is reading it as being 194f. The car is running fine aside from fuel consumption being above normal. The gauge on my dash is also showing that it's below normal temp. Any ideas?

 

Why did you replace the sensor in the first place?
What brand of sensor did you use?
You could clear the code and see if it comes back.
Wouldnt be bad to check the sensor is tight and the connection is good.
Considering you say this happen only after you replaced the temp sensor I assume something is wrong with it.

 

I got the code initially after the first time I replaced the vcg. So I tore it apart and inspected the sensor and noticed that it had some pretty severe damage. So I replaced and decided to replace my valve cover along with it since the mating area was damaged. After replacing both im now having the code p0128 thrown

 

Something I didn't answer in my first response is the fact that the replacement sensor is oem certified. Im wondering if i maybe over tightened it butbi also wasn't sure if that would cause issues 🤔

 

As far as I understand for this code, it sets if the engine coolant does not reach operating temp. My speculation is there must be some sort of clock programmed into the PCM that says not to set this code for a set amount of time after cold start/maybe every start up.

Start the engine cold and turn the ac off, watch the engine cooling fan, the fan should not run continuesly nor should it run for a unknown amount of time after cold start up as this would make it take longer to achieve cabin heat temp.
What you are looking for is if the fan is on, keeping the coolant cold.
Clear the code before doing this.

 

Do you think that if I over tightened the new sensor that it could cause an issue with the reading due to the depth?

 

I cannot say it is not possible, but considering the ford cylinder temp sensors are basically a copper/something bolt with two wires that determine the resistance of the copper/something as its temp changes with the engine temp, I am going to say that is very very highly unlikely that is the issue.

 

okay another question that might be dumb, after reading into it quite a bit I came across a site stating that the cylinder head temp sensor is also the sensor for coolant temp. True or false?

 

That is correct, for this engine there is only one temp sensor, the temp of the coolant is not something the PCM needs to view since it can be gauged from the cylinder head temp, the primary point of coolant is to keep the engine from overheating so if the engine starts to overheats it doesnt actually matter what temp the coolant is at since we know its not doing its job of keeping the engine from overheating.

I would watch the cooling fans when the engines running to see if they turn on and off like they should, the only time they should run continuously is if the engine starts to overheat the system does everything it can to bring the temp down.

 

Awesome I definitely appreciate the confirmation because I have been trying to locate a secondary sensor by going to my local junkyard and tearing apart another vehicle of the same year and motor in an attempt to figure this out