# Cooling fans continue running after engine shutdown



## Johnny B (Jun 4, 2019)

Cruzer4326 said:


> air filter replacement


Did you unplug the MAF sensor when you changed the filter?


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## jblackburn (Apr 14, 2012)

Johnny B said:


> Did you unplug the MAF sensor when you changed the filter?


This is the most likely cause if it doesn't happen again.


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## Cruzer4326 (Jan 22, 2017)

Johnny B said:


> Did you unplug the MAF sensor when you changed the filter?


Yes indeed


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## Cruzer4326 (Jan 22, 2017)

jblackburn said:


> This is the most likely cause if it doesn't happen again.


Ok, can you please explain to me how the ECM knew that I unplugged the MAF?
And then why did it run the fans like that?
I’m kind of a “ want to know why things happen “ guy…


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## Johnny B (Jun 4, 2019)

Cruzer4326 said:


> Ok, can you please explain to me how the ECM knew that I unplugged the MAF?
> And then why did it run the fans like that?
> I’m kind of a “ want to know why things happen “ guy…


Sure, the car is (for all intents and purposes) always watching its sensor inputs. So when you disconnected the MAF sensor, you interrupted the MAF signal and intake air temperature signal. So since the car doesn't know how hot it is, it defaults to assuming it is (roughly) 140F. And because of this is forces the radiator fan to run so the car doesn't over heat. 

People come on this site nearly everyday with similar issues. Same cause, but usually related to the two coolant temperature sensors.


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## Cruzer4326 (Jan 22, 2017)

Ok thanks for the reply!
I still don’t understand why the ECM would monitor those sensors with the engine off. But I accept your reply.


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