Fan does not work when coolant temperatures sensor is plugged in?

2009 CADILLAC STS

123,765 MILES • 3.6L • V6 • 2WD • AUTOMATIC

SMILEY1978

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I am having an issue with my fan not coming on. First, I changed the fan. Then I changed the fan resistor. Finally, I went to change the engine coolant temperature sensor and when I unplugged it the fan came on. Once I plugged it back in it would cut back off and won’t come on until unplugged again. Do you have any idea what is happening?

Jul 18, 2024 at 12:06 PM

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Yes, the system uses the engine coolant temperature sensor to monitor the engine temperature and turn the radiator cooling fan on accordingly. If the connection is broken the PCM will turn the fan on as a default to help protect the engine. I would swap the engine temperature sensor out to help fix the problem. Once completed start the engine and turn the A/C system on and wait about 1 minute and the fans should come on. Here are the instructions on how to change the sensor out correctly. Check out the images (below). Please let us know what happens.

Images (Click to enlarge)

Jul 19, 2024 at 11:34 AM