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Cooling fans on and dash temperature reads 160?

Tiny
UPMM019
  • MEMBER
  • 2015 CHEVROLET SUBURBAN
  • V8
  • 4WD
  • AUTOMATIC
  • 189,000 MILES
I noticed today on a drive back home. About a 30-minute trip that about 3/4 way into it that I could hear the cooling fans running. I then noticed the temperature at 160 on the dash.

When I got home the fans were still running and the dash still reads at 160. The fans ran for about another 5-10 minutes after the vehicle was shut off.

I drove the vehicle this past weekend for four 45 minutes trips and didn't have any issues and the temperature was over 160 but below the 210 mark. I never heard the fans run.

So, I am not sure what the issue is or where to start to troubleshoot it.
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Tuesday, April 16th, 2024 AT 8:47 AM

10 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 48,363 POSTS
Thanks for the video. wait until the engine cools down and then check the coolant level inside the radiator. If that is okay, I would do a CAN scan to see if any codes are stored or pending. You can get a CAN scanner (Controller Area Network) which will work on most cars from Amazon.

Here is a video to show you how:

https://youtu.be/u-4syLc-ifQ

and

https://www.2carpros.com/articles/can-scan-controller-area-network-easy

The temperature gauge and cooling fans are controlled by the PCM which if I had to guess is the problem. Here are the wiring diagrams so you can see how the system works. Also, I have included how to change the PCM out which you can get a pre-programmed unit by searching google or eBay. The PCM might just need an update from the dealer to help fix it. Check out the images (below). Please let us know what happens.

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Tuesday, April 16th, 2024 AT 10:34 AM
Tiny
UPMM019
  • MEMBER
  • 216 POSTS
So, you think the problem is the PCM or a temperature sensor? PCM seems like a real leap - I had figured it would be something more simplistic. I will check the coolant level, but I don't have access to a CAN tool. I have a cheap OBD II reader but that I only ever use if there is a check engine light. Mostly if check engine comes on this vehicle it's a o2 sensor error.
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Wednesday, April 17th, 2024 AT 5:11 AM
Tiny
KEN L
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  • 48,363 POSTS
I hear you, if the PCM thinks the engine is cold and it turns the fans on seems strange. We could try the coolant sensor to see if that fixes it, it could be a safety device.

Here is the sensor, also it could be the cluster as well, we might want to try a CAN scan to see if any other codes are stored. Here is the location of the sensor. Check out the images (below). Let us know how it goes.
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Wednesday, April 17th, 2024 AT 9:56 AM
Tiny
UPMM019
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  • 216 POSTS
Did you mean to say that the PCM thinks the engine is warm and turns on the fans. If the engine is cold, I am not sure why the fans would come on. Is there any budget scanner you could recommend?
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Wednesday, April 17th, 2024 AT 12:23 PM
Tiny
UPMM019
  • MEMBER
  • 216 POSTS
I just checked the coolant level, and it appears to be normal. As soon as I start the vehicle the fans come on. I tried looking at the scan tool I have but didn't see anything on there that would tell me anything about the sensors.
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Wednesday, April 17th, 2024 AT 5:51 PM
Tiny
UPMM019
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  • 216 POSTS
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Wednesday, April 17th, 2024 AT 5:52 PM
Tiny
UPMM019
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  • 216 POSTS
I have the Autel OBD2 Scanner.
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Wednesday, April 17th, 2024 AT 5:53 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
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Thanks for the video. Yep, that is not normal. The scanner you have will do engine codes only. You will need to upgrade the scanner to one of the more capable units or have a shop scan it for you. To me it sounds like an update for the PCM could fix it, but we will learn more once the CAN scan has been run.
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Thursday, April 18th, 2024 AT 10:07 AM
Tiny
UPMM019
  • MEMBER
  • 216 POSTS
Replaced the thermostat and temperature sensor. Issue is resolved.

Fans run when expected and dash temp now reads the range from cold to 210.

I didn't do a CAN scan since I didn't have the scanner for doing so.
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Wednesday, April 24th, 2024 AT 7:21 AM
Tiny
KEN L
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Glad you could get it fixed, thanks for letting us know. Please use 2CarPros anytime we are here to help.
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Wednesday, April 24th, 2024 AT 9:41 AM

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