Fans run like the engine is overheating, coolant gauge reads no temperature, A/C disengaged.

Vector

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My 2015 Escalade was running fine, but I noticed a loud hum under the hood. The fans were running much faster than usual, so I looked at my coolant guage and it was reading zero, despite me having driven for miles. I pulled over and under the hood the temp felt fine, hose barely warm to the touch, even the heat shield near the exhaust manifold barely felt hot.
I did not think much of it, then I received a message saying the A/C was shut down.
I got home, shut of the engine, but the fans were running at high speed and continued to do so, as if it was overheated, and needing additional cooling.

Being late at night, I didn't want the fans to drain the battery overnight, so I disconnected the battery. I called the dealership, and they said it sounded lie a sensor malfunction, or maybe the thermostat was stuck. For my Corvette, I know exactly where the temp sensor is, as well as the thermostat. On this behemoth, I have no clue where either are located.
In any event I decided to go out and examine the engine. Upon reconnecting the battery, and starting it up, everything seemed back to normal. A/C worked, fans on normal speed, and the coolant temp read a normal temp.

That was a couple of weeks ago, and I assumed the battery disconnect caused a re-boot if you will, and hoped the problem to just be an anomaly.
Sadly the problem started again with the exact same symptoms. This time I let the fans run after turning it off, and they ran for about 5 minutes, then shut off.
Now without a battery disconnect like last time, with a totally cold engine, if I start it up, the fans are going into high speed mode, despite the engine being totally cold. Thus I doubt the thermostat is getting stuck in the closed position, otherwise the engine would overheat.

So with all those symptoms being tied together, I am hoping others here have the knowledge of what it might be?
 

exp500

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Tha factory manual has a very good troubleshooting section. Ebay. Others here may have a recommended seller.
I would swap relays.
 
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Vector

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Tha factory manual has a very good troubleshooting section. Ebay. Others here may have a recommended seller.
I would swap relays.
No offense is intended with the following reply to your post.

Many of us do not need generic replies about checking factory manuals, or that we can buy information from Ebay, or Google is our friend.
When I see fellow posters who need assistance, if I have the ability to help them, I give as much information as I can.
I do not tell them to "read a manual" or "go to the dealership" as some non-informational reply.

In this case I am hoping a fellow forum member has experienced the same problem, and can give advice, so I do not make a generic mistake on what be a commonly experienced problem.
If anything, the most annoying reply to a members posting of their bad experience, is a fellow member asking "why didn't you ask here first, before spending $$$$ that should have only cost you $.

So thanks for your reply.
That said, I am looking for suggestions from those who might be familiar with this issue.
 

Tahoe14

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Vector, If you do a Google search and describe your symptom many times it will pull up truck forums like this one and the other popular one with a possible solution or what worked for what a person is describing as an issue so you don't have to wait and hope that you get a response. I have been helping members on this site and the other site for many years and have done many Google searches to locate and share the information that would help the poster, Google is your friend, LOL. Another example is folks are trying to figure out how to perform a repair and many times a Google search will bring up a you tube showing exactly what someone is trying to do. Just food for thought. Good luck with your issue and I hope you get it figured out so you can share the fix with others.
 
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Vector

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Vector, If you do a Google search and describe your symptom many times it will pull up truck forums like this one and the other popular one with a possible solution or what worked for what a person is describing as an issue so you don't have to wait and hope that you get a response. I have been helping members on this site and the other site for many years and have done many Google searches to locate and share the information that would help the poster, Google is your friend, LOL. Another example is folks are trying to figure out how to perform a repair and many times a Google search will bring up a you tube showing exactly what someone is trying to do. Just food for thought. Good luck with your issue and I hope you get it figured out so you can share the fix with others.
Well then tell me why even come to a forum like this, when the only two suggestions is to do what is obvious to most other people.
If this was a very active forum, someone might give such responses as a bump post to bring it back up to the top some someone with knowledge might see it.
But this forum seems like it is not frequented that often.

Yes I can go to Google or Youtube looking for answers, and at one point found something similar on another GM type of vehicle. Yet I had hoped to come hear to see if other fellow forum members who had the same type of engine I do (6.2 in the Escalade and Denali) might have some experience with this same issue and/or advice.

When I see a fellow poster asking for advice/help with something I know about, I take the time to give detailed advice or relay my personal experiences.
Not just say look it up elsewhere.
Yet to some it sounds like a robo bot could just come into every thread, and give a generic recommendation to "check the owners manual, Google the problem, or go look at Youtube videos for help".
Again, if that is the case, why even be a forum member and post here?

BTW - Though I have not fully figured out the issue yet, my ESV threw a code, and Autozone said it is (with their limitations) the thermostat.
Assuming it matters to anyone the code thrown was [ P0128 ] Coolant Thermostat (Coolant Temp Below Thermostats Regulating Temperature)
 

iamdub

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Well then tell me why even come to a forum like this, when the only two suggestions is to do what is obvious to most other people.
If this was a very active forum, someone might give such responses as a bump post to bring it back up to the top some someone with knowledge might see it.
But this forum seems like it is not frequented that often.

Yes I can go to Google or Youtube looking for answers, and at one point found something similar on another GM type of vehicle. Yet I had hoped to come hear to see if other fellow forum members who had the same type of engine I do (6.2 in the Escalade and Denali) might have some experience with this same issue and/or advice.

When I see a fellow poster asking for advice/help with something I know about, I take the time to give detailed advice or relay my personal experiences.
Not just say look it up elsewhere.
Yet to some it sounds like a robo bot could just come into every thread, and give a generic recommendation to "check the owners manual, Google the problem, or go look at Youtube videos for help".
Again, if that is the case, why even be a forum member and post here?

BTW - Though I have not fully figured out the issue yet, my ESV threw a code, and Autozone said it is (with their limitations) the thermostat.
Assuming it matters to anyone the code thrown was [ P0128 ] Coolant Thermostat (Coolant Temp Below Thermostats Regulating Temperature)

My bet is a faulty coolant temp sensor or a defective harness connector. I recently saw a YT video where a guy had your same symptoms on his Escalade. The sensor had failed, making the gauge read "0". As a failsafe since it has no idea what the actual coolant temp is, the PCM commands both fans on high speed and keeps the A/C off to prevent extra heat from the condenser. It also runs the fans for about five minutes after the key is turned off.

Watch the first eight minutes of this veideo:
 
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Vector

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My bet is a faulty coolant temp sensor or a defective harness connector. I recently saw a YT video where a guy had your same symptoms on his Escalade. The sensor had failed, making the gauge read "0". As a failsafe since it has no idea what the actual coolant temp is, the PCM commands both fans on high speed and keeps the A/C off to prevent extra heat from the condenser. It also runs the fans for about five minutes after the key is turned off.

Watch the first eight minutes of this veideo:
First of all, this video does help, as it mirrors my issue to the tee.

Second, and before some say "I told you so", I had tried to look up my issue on Google and Youtube (that is why such suggestions can be pointless), and as we all know, sometimes one key word missing or some other variable can cause different videos to come up, while others will not.
This video did not come up in my search, only a couple poorly done ones, without any detailed explanation of the issue, different engine, testing, etc.

So thank you for taking the time to post this video. :happy160:
I think I will replace the sensor, and see if that solves the problem, rather than replacing the thermostat. I will be back sometime in the near future to let others know of my results.
 

iamdub

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First of all, this video does help, as it mirrors my issue to the tee.

Second, and before some say "I told you so", I had tried to look up my issue on Google and Youtube (that is why such suggestions can be pointless), and as we all know, sometimes one key word missing or some other variable can cause different videos to come up, while others will not.
This video did not come up in my search, only a couple poorly done ones, without any detailed explanation of the issue, different engine, testing, etc.

I get it! I have decently strong Google-Fu. But there are times where I still get caught up not using the one magic keyword I need to pinpoint what I'm trying to find. I wasn't specifically looking for anything coolant temp sensor-related. I subscribe to LegitStreetCars and was catching up on the latest of his wife- I mean, the latest of his wife's supercharged Escalade. :p Your description of the symptoms reminded me of that video.


So thank you for taking the time to post this video. :happy160:
I think I will replace the sensor, and see if that solves the problem, rather than replacing the thermostat. I will be back sometime in the near future to let others know of my results.

A stuck-open thermostat would still allow the coolant to warm up enough to register on the gauge and not just sit at "0". The PCM isn't seeing ANY temp at all, so it's playing it safe. It's far better for it to over-cool than under-cool.
 

Doubeleive

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your symptoms are perfectly normal (fans running high speed and after the key is off, no ac) when the computer cannot get a coolant reading.
so like noted above
it's either the coolant sensor or the harness.
 

THarber

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I would first replace the coolant sensor and make sure all connections are tight. If you're reading "0" that's the obvious place to begin. The sensor is below the thermostat housing and can be identified by its brass base that screws into the block. Replace it with battery disconnected, reconnect and see what happens. If that does not work, there is a separate pressure switch on the high side a/c line that forces the fans to run anytime the a/c is on high. Make sure the connections are tight. Its not a replicable item unless you 1st void the system of freon, replace then fill it back up. There is no reason for them to fail so check connections 1st.
 

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