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No signal from coolant temperature sensor to E-Fan

Tiny
SOMBOYV
  • MEMBER
  • 2010 CHEVROLET SILVERADO
  • 4.8L
  • V8
  • 2WD
  • AUTOMATIC
  • 160,000 MILES
Hi everyone, my truck cracked a radio on the plastic ends. Well, this is when the headache started because I know there's a cause for that. So, I replaced the radiator, changed the thermostat, new antifreeze, and belt. I started the truck up and noticed the fan was not kicking on. Changed the coolant temperature sensor out with new harness because the old ones were corroded, still no fan. Turn the A/C on and the fans worked, but when sitting at idle with no A/C the fan will not turn on checked the cabled/wires no damaged then I notice with the truck on if I disconnected the harness from the coolant temperature sensor the fan would turn on, but when I plug it back into sensor it doesn't work. I really need you guys help on this. Thanks
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Monday, January 17th, 2022 AT 6:08 PM

23 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good morning,

What temperature thermostat did you use when you performed the repair?

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

The fan should kick on when you remove the wires from the sensor. That is the test for the wiring for the sensor. When the wires are off, it sends a high temperature signal to the ECM and the fan is commanded on.

https://www.2carpros.com/articles/replace-electric-fan-motor

What I am wondering is if the engine coolant temperature does not reach 208 degrees, the fan is not required to come on.

Does the engine temperature on the dash ever go high when the fan does not come on?

Roy
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Tuesday, January 18th, 2022 AT 2:06 AM
Tiny
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How you are doing? Roy, thanks for responding. But I replaced the thermostat with one from AutoZone that's rated at the 187 degrees and for the temperature sensor, the temperature gauge on the truck does reach 210 and above. And to double check that I have a basic scanner that I hooked up went to ect and confirms that ect temperature does rise starting from start which is -40.
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Tuesday, January 18th, 2022 AT 7:02 AM
Tiny
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The correct temperature for the thermostat is 195.

What is the actual temperature on your scan tool? I never believe those gauges.

Roy
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Tuesday, January 18th, 2022 AT 7:13 AM
Tiny
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It actually goes higher then 195 reaches up to 220 and higher, but I will turn the truck off to keep it from overheating, but when I did let it go past 220 I Will leave the reservoir cap off and fluid will shoot out when I turn the truck off and temperature is at about 230 and higher.
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Tuesday, January 18th, 2022 AT 7:31 AM
Tiny
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  • MECHANIC
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Did you replace the coolant sensor itself?

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

There is no electrical issue at all, the only thing is the sensor itself.

https://www.2carpros.com/articles/coolant-temperature-sensor-cts-replacement

Roy
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Tuesday, January 18th, 2022 AT 8:03 AM
Tiny
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Yes, the sensor has been replaced. I even bought another one just to make sure the first one wasn't defective.
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Tuesday, January 18th, 2022 AT 8:11 AM
Tiny
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There is a code for P0118.
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Tuesday, January 18th, 2022 AT 8:28 AM
Tiny
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Everything seems to be functioning as it should, just the fan doesn't turn on and the truck will overheat. I even tried the method of taking the old sensor hook it up and heated it up with a small torch and that activated the fan which was pretty quick.
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Tuesday, January 18th, 2022 AT 8:34 AM
Tiny
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Okay, 118 is for when you pulled off the connector at the sensor.

I still think you need a 195-temperature thermostat.

Roy
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Tuesday, January 18th, 2022 AT 8:47 AM
Tiny
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Okay, I will go pick one up today and get back with you.
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Tuesday, January 18th, 2022 AT 9:01 AM
Tiny
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Keep me updated.

Roy
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Tuesday, January 18th, 2022 AT 9:20 AM
Tiny
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There's no thermostat for my model truck that is rated for 195. There is a 190. Question, if my temperature gauge on truck is working and my scanner has a temperature reading and the temperatures or over heating temperature, but my fans still doesn't turn on. Why am I changing the thermostat?
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Tuesday, January 18th, 2022 AT 9:36 AM
Tiny
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It may not be fully open, allowing circulation.

How high does the temperature get before you turn it off?

Roy
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Tuesday, January 18th, 2022 AT 9:43 AM
Tiny
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220-235.
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Tuesday, January 18th, 2022 AT 10:40 AM
Tiny
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Just changed the thermostat out with a rated 190. Is all that anyone carries around here. Electric fan still doesn’t turn and on temperature reached about 218 before I cut the truck off and that's reading off of my scanner. Checked my grounding visually and with instrument as well.
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Tuesday, January 18th, 2022 AT 11:10 AM
Tiny
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Okay, let it run again. Let it go to 220 and see if the fan comes on. Damage happens after 235 so 220 is good.

Roy
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Tuesday, January 18th, 2022 AT 2:04 PM
Tiny
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Doing that now. I will keep you updated.
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Tuesday, January 18th, 2022 AT 2:13 PM
Tiny
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Sounds like a plan.

Roy
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Tuesday, January 18th, 2022 AT 2:16 PM
Tiny
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No fan truck temperature reached about 238 before shutting off. And the fan never came on.
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Tuesday, January 18th, 2022 AT 2:55 PM
Tiny
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Let me check for any TSB or recalls.

Roy
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Tuesday, January 18th, 2022 AT 3:06 PM

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