Help Diagnosing a 2006 Ford Fusion?

[jhammel85]

I have a friend that owns a 2006 ford fusion SE, 4 cyl, auto...

Their check engine light came so I checked it for codes. I got a code saying that the engine temperature below threshold. I wish I had the number on hand but I dont....anyway, I believe it would be the temp sensor for the ECU unless maybe it would be the thermostat. I dont think its the thermostat since it heats up great, does not get hot, and has great, constant heat inside the car.

So, I want to fix it for them but I would feel terrible if it was not the engine temp sensor...You guys have any advice? Would you agree that it's this sensor? Hopefully some professional mechanics on the forums can help?!

 

[Earl43P]

Sounds like the ECT sensor, just like you said.

 

[Sasquatch_Ryda]

Was it a KOER test? If so...was the vehicle up to operating temp?

 

[adsm08]

Yeah, if the engine wasn't at temp then that isn't a valid code.

 

[naford]

Does it have a gauge on the dashboard or is it an idiot light? How long has the CEL been on? Who read the code?

 

[jhammel85]

Yeah it was read by a code reader. I did it myself with one that we have at our shop at work. Sorry, I forgot to mention that yes, it was at operating temp and the check engine light is on (dont know how long). Car seems to be functioning perfectly as it should. Its just that the light is on.

Thanks for everyones input so far!

 

[adsm08]

In that case I'd start by replacing the sensor. They aren't that expensive.

 

[jhammel85]

Alright well, I cleared the code for my friend 2 weeks ago and it just came back.

I ran for codes again and I got the same 2 as last time...Both are the same:

PO128 - coolant Temp Below Thermostat Regulating Temperature Threshold.


Now, I'm wondering if its the thermostat because maybe the code means that the engine did not get up to temp in the right amount of time. The reason why I would suspect the ECT is because the car has great heat. Gets up to temp perfectly fine and stays in one spot once it does.

 

[adsm08]

Its the t-stat. My dad's 06 Explorer threw this code about a year ago. I watched the temp PID and then checked the t-stat specs. The temp topped out 2* below the thermostat spec.

 

[jhammel85]

Great! Nice and easy fix. We'll start there. Thanks!

 

[adsm08]

Yeah, that code means that the computer is not seeing the coolant ever getting as hot as it should. Usually means the t-stat has stuck open.