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Here is a picture of the sensor, the thermostat assembly and the location of both the thermostat housing and sensor located right beside the housing. it it kinda hidden under the intake on the passenger side. The thermostat house runs from the passenger side to the drivers side and then 90's and head toward the radiator and attaches to the upper radiator hose. Maybe if you can find the upper radiator hose and follow it, you can fin where the thermostat housing is, and the sensor is literally about 1 inch from it..
Also, i guess i should add, i have a 2017 Acadia Denali, and apparently there are two different motors in that year, depending on which one you have, the other engine that is different than the one I have, the sensor is located in the front of the motor down low.
 

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Also, i guess i should add, i have a 2017 Acadia Denali, and apparently there are two different motors in that year, depending on which one you have, the other engine that is different than the one I have, the sensor is located in the front of the motor down low.
So . . are you saying that you have a 2017 Acadia Denali "Limited" Old Body Style? . . . It has the battery mounted below the floor in the rear of the vehicle.
Or do you have the newer smaller Acadia where the battery is under the hood with the engine.?

They made botht he older style Acadia and newer sytle in 2017. The older style was called the Limited. .. . look that up on the internet and maybe include that in your fourm signature with the "Denali" you now have there..
 

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The 2017 Limited is NOT a Denali. The two shouldn't be confused. The Limited is an SLT-based Lambda platform Acadia.
 

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Of course and understood.
It may be confusing to some including the OP. He just mentions "two engines".
Regardless some such as OP may not know about the Lambda vs C1xx platform change.
At any rate. . if the battery is below the rear floor. . . that would make it Lambda based old platform.
 

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2017 Acadia Denali 3.6, Just had same issue, coolant temp reading 0, fan running full speed, steering assist reduced warning. I first replaced thermostat, which is doable, but not an easy task. Located on top of motor passenger side. Have to pull air Intake to get to it. Able to separate radiator intake pipe at the thermostat housing elbow and did not have to pull the fuel rails.

This did not resolve the issue. I then had to tear it all back apart to change the engine coolant temperature sensor which is located right next to thermostat housing. I suggest if you change thermostat just go ahead and replace this, as it is $15 and not much work while you have it torn apart. Dealer wanted $900 to replace thermostat. Took me 3-4 hours and cost $175 for both thermostat and sensor. Took 2 hours the second time I tore it apart for the sensor. After all that it did not resolve issue.

I then saw where one guy had battery cable replaced and I really just thought it may be a ECM issue at that point. So I went out and unplugged negative battery cable for about 10 minutes to reset ECM. And that worked, for now anyhow.

I’ve had several other electrical glitches with this car, like door locks not working right, brake lights staying on, etc. So I’d say if you are experiencing any issue with the 3.6 engine Acadia, unhook negative battery cable for 10 minutes which reboots ECM. Now here’s hoping that my issue does not come back and that this solution helps someone else.
The Engine coolant sensor is right next to the thermostat housing. It is on passenger side, on top center of engine. If you stand on the passenger side fender well, you can see both the thermostat housing elbow and the sensor. If you are having these same issues, you should try disconnecting the negative battery terminal for 5 minutes or so and see if this fixes your issue.
I have a 2017 SLT that was having the same issues. So before diving into the whole ECT sensor/Thermostat pool I decided to look at the battery terminal issue. I found a bit of corrosion around the negative terminal, I removed the terminal and cleaned it really well and replaced it. Its been about a week and that seemed to solve the issue, so anyone having this problem I would try this first. It may not be the same for everyone but it seems to be working for me. Also I found a GM service bulletin on this issue, it says it may be the sensor but may also need an ECM software update. The electrical issue may be the cause of a lot of the headaches people seem to be having with what seems to be a common problem. Here's the service bulletin # if anyone is interested 17-NA-390.

(mod edit: added link to cited bulletin)
 

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Ok. My 2017 acadia has been doing this intermittently off and on for a year. Lasts about a week. It just started doing it again today. So after reading this forum I tightened the negative and positive battery terminals without removing them and it didn't help. I tried staring it a couple more times and it still gave the power steering assist message and no a/c. So then i took off the negative terminal and cleaned it. Than i took off the positive terminal and cleaned it. Tightened the fuses next to it also. Put positive back on and tightened. Than negative back on then tightened. Sprayed battery protection on them. Started it back up and everything works again. I tried starting it 3 more times and it works great. I think the terminals are the ticket. Just wanted to share my experience
 

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Ok. My 2017 acadia has been doing this intermittently off and on for a year. Lasts about a week. It just started doing it again today. So after reading this forum I tightened the negative and positive battery terminals without removing them and it didn't help. I tried staring it a couple more times and it still gave the power steering assist message and no a/c. So then i took off the negative terminal and cleaned it. Than i took off the positive terminal and cleaned it. Tightened the fuses next to it also. Put positive back on and tightened. Than negative back on then tightened. Sprayed battery protection on them. Started it back up and everything works again. I tried starting it 3 more times and it works great. I think the terminals are the ticket. Just wanted to share my experience
Did this work for you? I have a 2017 Acadia Denali and after reading everything on this forum I have taken both positive and negative cables off and removed all corrosion. The car would run great for about a week and then the corrosion would return and we would have to do the same thing again. It's mostly on the negative cable. I'm wondering if I have a bad battery... any thoughts?
 

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To everyone in this forum: After a year of headache, I finally figured out what the issue is. Yes, it is the thermostat, but you have to get it replaced from the dealership with the newer thermostat that GMC came out with after many complaints. The old replacement part that you get from AutoZone or even the first dealer I went, is the problem in the first place. There is a new updated thermostat GMC came out with to directly solve the issue for good.

Also, with all the wear and tear that it does on your vehicle while the bad thermostat is going bad. It drains your battery, completely kills your battery. In that case once you do get the right new thermostat your car will begin to go haywire and start throwing all these codes, not wanna start, and you kind of feel like you’re back at square one. No, you actually know at that point that you have solve the problem and what it’s doing is it shutting down everything in your car and going into battery saver mode because your battery is damaged and can’t withstand all the features that your truck has.

You’ll go to AutoZone to check your battery they’ll tell you your batteries good yes your battery is good but it’s not good enough for your vehicle with all the bells and whistle‘s and steering assist, touchscreen, power seats and every feature this truck has. You have to go get a new battery after getting the corrected new thermostat from GMC.

P.S. THIS IS COVERED UNDER YOUR POWERTRAIN WARRANTY AND THE THERMOSTAT WAS FIXED COMPLETELY FOR FREE AT THE SECOND DEALERSHIP I WENT. THE FIRST DEALERSHIP ****ED ME AND CHARGED ME WHICH IM IN THE PROCESS OF GETTING MY MONEY BACK FROM GMC FOR THAT OUT OF POCKET COST THAT WAS COVERED UNDER THEIR WARRANTY. Hope this helps everyone out there!
 

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Also I went ahead and bought a top of the line Optima Battery with 800ccc. Cost me about $350, but it’s got my truck driving like a dream come true, has more power than ever, and was worth every copper penny.
 

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How is it your thermostat when it does it at first start up? Engine hasn't even started to get warm yet. Very first thing that comes up. A thermostat doesn't even start to work until the engine gets upto 180 degrees or whatever its set at. Its an electrical issue im convinced. Battery terminals or computer. But taking off the terminals always resolves the issue.
If your battery is getting corroded than it might be leaking gases internally.
 

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How is it your thermostat when it does it at first start up? Engine hasn't even started to get warm yet. Very first thing that comes up. A thermostat doesn't even start to work until the engine gets upto 180 degrees or whatever its set at. Its an electrical issue im convinced. Battery terminals or computer. But taking off the terminals always resolves the issue.
If your battery is getting corroded than it might be leaking gases internally.
I think you read my post wrong, re-read to answer your own question.
 

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My battery is new and i haven't had any problems with it either. No other codes.. Hope everything is good for you.
 

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new to forum but not to the car game. I have been dealing with this same issue for a little over 1 year.. after reading thru the thread I realize no-one is finding the common instigator of the issue. I have determined what causes the message to pop up, fans to run, a/c to stop running and general chaos that happens when your wife is driving along and things go to crap.

Ours is a 2017 SLT and the only time it comes on is when the outside temp is under 65 Degrees F. then the fun begins.. I have had it start anywhere from 2 to 20 miles into a cool temperature drive. it is easy to make the situation end buy disconnecting the battery for 30+ seconds. it will make it all stop until you have a cold weather drive (i know in many places of the world 65 F is NOT cold.. but it is here in Cali lol).. once you have this temp event the whole thing starts over again... I am finally breaking down and going to the stealership tomorrow, i know they are going to try and make me bend like a pretzel and take my credit card for all it is worth but, I am tired of my wife hiding my 10MM wrenches because she can't find one (10mm the hardest size to keep in your toolbox).

Things I am taking away from this thread are as follows, a potentially redesigned thermostat, sensors are a pain in the azz to locate (yes I have tried as well and gave up), and no-one is 100% on a specific repair for the problem but the symptoms have been getting handled (all the things that happen when the message comes up).

If anyone can look into their personal history with this issue and confirm that it only STARTS when it is colder then 65 please let me know...once the error starts it doesn't normally go away although I have seen a couple rare instances when it went back to normal by itself.. normally it requires a system reset (battery disconnect) to clear the issue. well here we go... to the stealership and hoping it's not going to hurt...maybe i'll bring some lube just in case they don't offer any..

As a side note, in my setting up the appointment i started grilling the service guy about possible issues and he instantly homed in on the thermostat housing. I am aware of a potential TSB addressing the calibration of the temp system and i'm hoping for to just need a calibration flash.
 

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I actually had my thermostat replaced abouta month ago, under the factory warranty.. It's been fairly cold the past couple weeks here, and no error had come up yet.
 

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got home from stealership... glad i brought the lube because this is painful.. apparently you have to remove the intake manifold to access the thermostat!!! this repair is going to involve replacement of the thermostat, housing (thermostat is built into the housing and requires the replacement of both), sensor, and the fluid. i found a video that shows the thermostat service being done (
)... i had to look it up because i felt like the stealership was pulling the most insane con job on me when he told me the manifold had to come off. in the video he says GM made a change on the newer models and moved the thermostat to the driver's side of the engine by the radiator hose, but alas i have an early build 2017 model so mine is buried under the manifold... for the price i am paying for this service it had better fix the problem!!

so lets check something else out, anyone who is having this issue what is the build date on your car? i'll grab my build date off the label when i get her back from the dealer.
 

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got home from stealership... glad i brought the lube because this is painful.. apparently you have to remove the intake manifold to access the thermostat!!! this repair is going to involve replacement of the thermostat, housing (thermostat is built into the housing and requires the replacement of both), sensor, and the fluid. i found a video that shows the thermostat service being done (
)... i had to look it up because i felt like the stealership was pulling the most insane con job on me when he told me the manifold had to come off. in the video he says GM made a change on the newer models and moved the thermostat to the driver's side of the engine by the radiator hose, but alas i have an early build 2017 model so mine is buried under the manifold... for the price i am paying for this service it had better fix the problem!!

so lets check something else out, anyone who is having this issue what is the build date on your car? i'll grab my build date off the label when i get her back from the dealer.
Thanks for the feedback. Wow. . what an ordeal just to change the thermostat.
 

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yeah it's crazy. the service has been completed but i need to test the car with the outside temp conditions in the range i know it triggers the problem with to make sure it actually fixed the issue.
 

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If you don't trust the dealer, like the pricing, or want to tackle it yourself, why not go to an independent mechanic? There shouldn't be any programming needed for this work.
 

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If you don't trust the dealer, like the pricing, or want to tackle it yourself, why not go to an independent mechanic? There shouldn't be any programming needed for this work.
i was told there could be a calibration issue so it could have been a programming issue..in general i don't trust shops but once it was completely revealed that the manifold had to be removed i was not going to take the risk of breaking the plastic manifold and do it myself. The car has 105k miles on it so plenty of heat cycles that could potentially make the plastic brittle.
 

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The latest update. My 2017 acadia started getting the power assist message and temperature gauge drop everyday. So when i get home i would keep taking off the negative battery terminal and retighten it. Clear the fault and drive again. I finally realized that i was tightening it down to tight and put a groove in the battery terminal. So as i was driving the negative terminal would loosen just a bit and the message would pop up. The last time after a week of dealing everyday with it i installed the negative terminal in a different spot off of the groove and torqued it down to correct value. Now for the last month or so i haven't had any more issues. Makes me think it was the terminal the whole time after dealing with it everyday. It was always tight enough to start and run the other systems but still loose enough to throw up the message and shut down the air conditioning.
 
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