Radiator Fan p0128 code?

2003 MITSUBISHI LANCER
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LEOMN21
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check engine light is on p0128 code thermostat mal.ok...im a student im just learning this.. my fan is always on when i start the car...and also after my car has been on and i turn it off i realize the fan goes on and off on the on position like if the car was running what can cause this problem?
Jun 24, 2009 at 8:48 PM
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SQM
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Hello,

That code P0128 is related to the coolant temperature sensor.

DTC P0128 : Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)

It is likely that the coolant temperature triggering the fan to run for longer than it supposed to.

You might find these articles helpful:

https://www.2carpros.com/articles/how-a-coolant-temperature-sensor-works

https://www.2carpros.com/articles/how-an-electric-cooling-fan-works

I have attached the diagnostics for that code as well as coolant temperature testing procedure for you reference.

Please let me know of any questions.

Thank you.
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Aug 3, 2021 at 7:03 AM
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