2015 Yukon XL temp gauge at 0 and radiator fan running constantly

So, we just drove home and I was noticing as we were driving, the radiator fan was really loud. As we got closer to home, I noticed the temp gauge was basically all the way to cold like the car wasn't running. I was told once that the temp of the engine is measured by coolant and, if you don't have coolant, the car will read cold yet overheat. But, I opened the hood. The radiator overfill has plenty of coolant. The engine wasn't hot at all. It wasn't like I opened the hood and tons of heat was present. But, the radiator fan ran for probably 5 minutes after I shut off the truck. I'm thinking maybe the thermostat... but why wasn't the engine burning hot when I opened it if the thermostat was stuck closed? Any ideas what this is?

Your thermostat could be stuck open or and probably more likely your coolant temp sensor has failed. When it fails the ecu goes into a protect mode and acts as if the engine is overheating.

... your coolant temp sensor has failed.

That's the first place I would look. Unplug the CTS and measure the resistance to ground. The indication should be reasonably close to this:

http://www.wwdsltd.com/files/CTS-MAT.gif

If the temp sensor had failed, shouldn't it have thrown an error on the dashboard?

Where is the temp sensor?

If the temp sensor had failed, shouldn't it have thrown an error on the dashboard?

Not necessarily.

Where is the temp sensor?

It's on the front of the engine. I found a YouTube video of a 16 XL with the 6.2. The guy talks about what happened and his symptoms are exactly the same as yours and he shows where is is and talks about the disconnection process.

https://www.youtube.com/watch?v=LPVYpqSLnn8

Ok, so I replaced the coolant temperature sensor and the problem is still there. Now my check engine light is on. I plugged my scan tool into the car and I have 4 codes. P0118 Engine Coolant Temperature Sensor Circuit High Voltage PERMINANT P0128 Coolant Thermostat (Coolant Temperature Below Thermostat Regulating P0118 Engine Coolant Temperature Sensor Circuit High Voltage PENDING P0118 Engine Coolant Temperature Sensor Circuit High Voltage CONFIRMED

Ok, just watched a Youtube video and it says sometimes I need to manually erase the code. So, I'm going to go try that.

Ok, so for whatever reason, my scan tool could see the code but I kept telling it to erase the codes and it would tell me 2 codes remain or something like that. I think it said 5 and then kept decrementing. It was only deleting one code at a time. But, then it got down to 2 and wouldn't go any lower. Seems like even if the problem was still there, it would delete the code and the next time the car started up, it would then re-fire the code. But, I was thinking maybe I don't have a good enough scanner. So, I was going to drive it to autozone to see if their tool could do it or buy a more expensive scanner. But, on the way there, I noticed the fan turned off and the temp gauge started working. I know cars usually clear codes themselves when the problem is fixed and you drive it for a little bit. So, I guess that worked here. So, I think I'm set. Thanks all!

Even with the engine off/ignition on, if the PCM does not detect a correct range signal an error code will be set. If you got it to clear, that is good. If it repeats, check the connections to the CTS and wire harness.

BTW - I saw that your Griffins dropped a 19U Tier II final round game to Boston yesterday. They had a really good run up to that point.

So, I replaced the coolant temp sensor when I made this post and it fixed the problem. But a half a year later, it's broken again? Coincidence or is something else causing it to fail?

You can measure the resistance of the CTS, and while in there inspect the sensor's connector and wire harness.

Ok, so replaced the coolant temp sensor again and it's back running normal again. Weird it went bad so quickly.

Ok, so replaced the coolant temp sensor again and it's back running normal again. Weird it went bad so quickly.

So, lasted a few weeks and broke again. ill have to look at the resistance. So, if the resistance is outside normal, how do i fix it? I looked at the harness a few weeks ago and it looked good to me...

Also, how do I read the chart? I'll be working on the car when it's the temp outside, so the engine will be about the temp is outside. So, it's usually around 40-60 degrees everyday. That would put me in the 40 - 70 degree range which would read 7500 - 3400 ohms. That's a pretty big range.

So, lasted a few weeks and broke again. ill have to look at the resistance. So, if the resistance is outside normal, how do i fix it? I looked at the harness a few weeks ago and it looked good to me...

Also, how do I read the chart? I'll be working on the car when it's the temp outside, so the engine will be about the temp is outside. So, it's usually around 40-60 degrees everyday. That would put me in the 40 - 70 degree range which would read 7500 - 3400 ohms. That's a pretty big range.

You're reading the chart wrong. It's not outside temp, it's the temp of the coolant. Just Google how to test a coolant temp sensor. I use a bowl of water cold, then hot measuring the water temp.

You're reading the chart wrong. It's not outside temp, it's the temp of the coolant. Just Google how to test a coolant temp sensor. I use a bowl of water cold, then hot measuring the water temp.

Ok, I found this video...

https://www.youtube.com/watch?v=SGz44I90XcE

It's basically having me take the coolant temp sensor outside the car and dipping it in ice cold water that I know the temp and checking the resistance. All this test is going to tell me is if the coolant temp sensor is bad. But, I've replaced it twice. What's the chances of buying two defective temp sensors? Seems to me, I've replaced the temp sensor. It's almost guaranteed fine... it's brand new. So, if the sensor is fine, what else could be wrong?

You buying aftermarket or OEM? That's all I can think of.

I don't remember for sure. I can't see how I have the original temp sensor and now two replacement temp sensors all gone bad and all have been a separate issue. Seems like if the temp sensors keep failing, something else in the car is causing it to fail... maybe something sending it over voltage and frying each one.... or if I'm looking for ohm resistance, maybe too many volts or amps going through it causing the resistance over time to decrease. But, the last sensor only lasted about 2 weeks.

Ok, I found this video...

https://www.youtube.com/watch?v=SGz44I90XcE

It's basically having me take the coolant temp sensor outside the car and dipping it in ice cold water that I know the temp and checking the resistance. All this test is going to tell me is if the coolant temp sensor is bad. But, I've replaced it twice. What's the chances of buying two defective temp sensors? Seems to me, I've replaced the temp sensor. It's almost guaranteed fine... it's brand new. So, if the sensor is fine, what else could be wrong?

The chance of buying two defective sensors are high if you're buying BDW or some other off brand.

The chance of buying two defective sensors are high if you're buying BDW or some other off brand.

But, it would be 3 defective sensors. The original and then two replacements. I think both of the replacements are Duralast.

But, not two, but 3 of the sensors have gone bad in a row. What are those chances? Seems like something within the car is messing it up.

But, today I drove the car again and it drove fine. So, it's odd... maybe a fluke. (Doubt it...) But, it seems to be intermittent.

Where does the wire from the sensor run to? Maybe I should check the resistance from the connector to the other side. That should be basically zero resistance of the connector and wiring harness if resistance with the sensor is what is determining the temp.

How many miles were on the original?

How many miles were on the original?

About 100,000 miles.

Then no it's not odd that it failed. Duralast is on par or worse than BWD when it comes to electric sensors. I still 100% believe your issue is bad sensors and not bad wiring.

Another consideration is the installation of the CTS. The threads should be sealed with a coating of anaerobic pipe sealant before assembly, then installed with a torque of 15-18 ft/lb. Excessive torque could potentially distort the sensor body and ultimately affect the sensor bonded into it.

So, it's been a couple of days and the problem hasn't happened. I haven't done anything to try to fix it.

My profession is IT. When I was in school, I took a computer repair class. I'd taken other ones in the past, but it was a required class to get my associates in the degree I was pursuing. I tried to get out of it... I had my A+ Cert already. But, I was very thankful afterwords that I did take the class.

All other troubleshooting I learned before then was, I saw a problem, I then took an assumption of what the problem was and then I replaced that part and looked to see if the problem went away. This class was different. Unlike most computer repair teachers, this teacher had a background in electrical.

We were not allowed to just swap parts to see if it worked. We had to look at the symptoms. Run tests. Then have concrete evidence between all of the tests we performed of what the problem was and we got one chance replacing the part to see if it fixed it. We had to get it right on the first try.

There are two schools of thoughts. Throwing parts at it until it's fixed. The other is logically diagnosing the problem. I've had 3 temp sensors and all have failed. I don't believe for a second I had 3 defective sensors. Also, since the problem has magically gone away in the last few days, the problem is very intermittent... doesn't quite jive with a faulty sensor.... you'd think it would do it all the time.

The only test that anyone has showed me is to test if the sensor is working. But, what are the tests to test the system all the way through? That's what we were taught in that computer class. You started from one end of the system and checked every component in one direction very methodically eliminating every component from the input to the output. There can't be only one test for this problem.

The sensor is checking the temp of the coolant right there. But then the wire harness is measuring resistance. But, where do the wires run to? What is the next component to verify? Also, probably need to test the wire harness all the way through in case something is wrong with that throwing resistance off.

You can doubt failed sensors all you want, but it doesn't make you right. Coolant sensors fail on GM's. I've seen it numerous times myself, and I don't even work on cars for a living. Cheap sensors (ie Duralast and BWD) are known for high failure rates. I've seen people have a Mass Airflow sensor fail on their car, replace it with a BWD, only to have another failure a week later. They get convinced they have some kind of wiring problem, until someone tells them to go to a junkyard and grab a sensor off a car there, only for it to fix their issue entirely.

Don't get me wrong, I am all for proper diagnosis, but this is a simple sensor. The only thing that is going to cause it to fail is age, or poor build quality.

Have you figured out this issue? I am having the same issue on my 2015 Yukon XL. We replaced the temp sensor with a new one from the dealership so not an aftermarket & the issue still exists, intermittently just as you described!

So, since replacing it again, it hasn't came back yet. It's been a few weeks now. This failing so many times though killed my battery so I had to buy a new battery. If you're also having this issue, also have a ratchet set so you can take the battery terminal off to stop your battery from dying. I bought a toolkit to keep in the back of the truck as well as the biggest battery jumper as well as the longest jumper cables that o'reileys sold. So, hopefully I'm never stranded again.

The failing sensor didn't kill your battery.

The failing sensor didn't kill your battery.

Yes, actually it did. When the sensor fails, the radiator fan runs at full speed like the car is overheating. When you shut off the car, the fan continues to run at full speed for at least 15 minutes. It drains the battery. You drain your battery completely dead too many times and you need to replace it.

If it happens again, I have tools in the truck now so I can disconnect the battery to save it.

If the fan running for 15 minutes killed your battery multiple times, then it was already on its way out.

Any updates on this?? Our truck is doing the EXACT same thing. We've replaced the sensor 2 times already. It'll work intermittently.

Quit buying junk sensors. If you read the thread the last post about the sensor said it was good to go.

I Got this issue with 2015 GMC yukon, the first sensor i got is autozone brand which failed after one month, second one i bought from GMC dealer which failed after 3 days, i am suspecting it could be a faulty ECM, i am doing the scope test tomorrow to confirm if its ECM or the wires.:screwy:

I am very interested in following this. I have a 2015 Yukon XL and have replaced the TCS three times.

It is intermittent. Will run for a few weeks and then the temp goes to 0 and fan runs. Then it will go another week. Seems like it happens more when driving on surface streets.

Can the wiring harness be replaced without removing an entire harness? Where can I check the resistance up the line further.

Someone mentioned the ECM, where is that at? Just real frustrated I can't fix this!

I have had this same issue with the fan running and the gauge showing 0 temp. The dealer said it was the thermostat getting stuck open which was completely wrong. I found that this happens when the voltage is a bit low. If I take it on the fwy and step on it the V goes up and the temp indicator turns on and the fan shuts off
Still don't know why I'm having the V issues.

As with many vehicles of this lineage, it's usually informative to check the reference voltages to sensors in the PCM harnesses underhood, as well as grounding. A 2015 model may not be old enough, but many older vehicles can develop issues with the connectors at the PCM itself, and disconnection/inspection/reconnection can resolve some of those problems.

As of now, this universal problem is unresolved.

I have this problem too, but I can’t replace the sensor myself. Once, the problem went away, then came back on its own. I paid $140 to get the sensor replaced, lasted about 3 months. These type of sensors are not intermittent. If you look at this problem in its entirety (read comments), there is no real data to digest this problem. So, I will start. I will again replace the sensor and get the “failed” one from the repair shop. Then I will test the resistance. I will record the effort. Some say they used OEM sensors and still have this problem. So it seems NOT to be a cheap sensor issue. There are other possibilities, perhaps unlikely, but car manufacturers have been caught doing hijinx, such as peppering emissions data (VW and others). Perhaps GM has purposely caused this problem. A voltage spike might kill a sensor. I am not saying this happened, but with a problem like this, thinking outside the box might resolve this. Learn how to measure resistance.you can get. Voltmeter from harbor freight for $7.99.

I will start by disconnecting the battery, clearing codes and observations. Then, replace sensor, correctly check resistance. If the resistance is off, then is the sensor cheap or is there a voltage spike killing it. I do not have a voltage logger, to monitor the voltage. I wish I did.

The large number that have this problem, bad sensors, loose connectors, bad computer, with all you experts, you would think this one would be easy. If you still believe it is cheap sensors, then it should be easy to prove (intermittent cheap sensors? I doubt it). Let’s gather some data to make the solution more definitive (says the new member).

The only potential "planned obsolescence" may be from the wire harnesses used in vehicles. The massive push to lighten vehicles, provide excessive automation and monitoring, be "environmentally conscious", and reduce build costs could have resulted in less robust wiring. It may not happen as frequently in Georgia, but in the Rust Belt of the midwest I've seen multiple examples of wiring failures, often with crimped connections, and all resulting from oxidation, overload, and corrosion. 18 gauge wire fused at 10A or more, no solder on bussing and interconnections in fuse panels and UECs, and literally dozens of wires bundled into looms which are intended to flex and move with the engine and suspension.

What could possibly go wrong after the warranty expires?

There reason there is a "large number" is because there are a metric shot ton of these vehicles on the road. Also forums are where people come to post about when they have problems. No one posts a thread when their vehicle is running good.

Well, despite my long winded rant this morning, I got in my 2015 Yukon Denali XS and as expected the fan was blaring at cold temp (just started from overnight). I drove about 3 miles, no engine temp. After being in the store for 20 minutes and coming home, I noticed engine temp was reading but check engine light on. By the time I got home - 2 more miles, the check engine light is off. Oh well, my science project will have to wait until next time.

On an earlier Yukon model, my brake switch was faulty (also a universal problem) and I replaced it. I looked at the failed one carefully and could not see the problem with it, despite being a mech engineer with over 30 patents. Sometimes small imperceivable things can contribute. I suspect wiring for the eng temp problem too. It is VERY unlikely that cheap sensors will come and go, besides many reported using OEM switches with the same bad results. The clue here people is intermittent.

I have been dealing with same problem on a 2017 Denali. Replaced sensor with acDelco only to have same problem a week later. I checked resistance on both sensors and they read the same. Checked wiring and connector and they all seem fine. Anybody have any luck or an update on what fixed this problem on their vehicle?

Here is my experience with same symptoms. I replaced the sensor and the connector. It worked for a couple days and then went back to low temp reading and high fans. I have disconnected the battery long enough for the computer to reset, and it goes back to working again immediately. I have done this several times now, and it always starts working immediately. One time it kept working through a 600 mile road trip. Another time, it only worked for 20 miles. I'm only 3 weeks since replacing the sensor, so not sure how many times I will have to keep resetting the computer.

It has been a few weeks since I posted my response, reporting my intermittent low temperature reading causing the fan to run (protection mode) in my 2015 Yukon Denali. It went away for a while and recently came back. This thread has not convinced me that anyone has figured this out. I refuse to replace the sensor with a aftermarket or OEM sensor. In my experience, it is very unlikely that sensors are intermittent. Couple that with the reports here, where the exact problem occurs with “cheap” sensors and OEM sensors and repeats soon after replacement. Logic should tell you that the problem is not the sensor, a) if it is intermittent and b) problem still occurs with “cheap” OR OEM sensors.

For me, the most logical would be a bad connection or a voltage spike. How do we resolve this? The only way I would go is to monitor the voltage realtime (as has been previously mentioned). I will look into how to do this cost effectively.

Meanwhile, are there any detriments (besides battery usage) to running in protect mode?

Don't be too surprised that if you ever get to the resolution of the problem, you may find several failed or failing wires in a harness. That's nothing new around here.

http://www.wwdsltd.com/files/PCMWireHarnessWear.jpg


Look closely, and the other wires which are in the process of failing become apparent. You won't find this with a scanner, nor a meter. It requires functioning neurons, which is why dealerships' service departments throw in the towel and tow vehicles off to specialists.

The SAME thing can occur at the connectors for the PCM, at a BCM, the IP, and bulkhead.

Bear in mind that the Delphi system uses a 5V reference regulated in the PCM as a supply for the peripheral sensors. Those PCM inputs are frequently loaded by a 2.2KΩ resistor to somewhat isolate the inputs and protect the 5V supply from overload. If you understand Ohm's Law, that means that the current flowing in a given sensor circuit is extremely low. That also means that any additional resistance will have a significant effect on the resultant signal.

In a nutshell, a corroded connection or broken down wire might show general continuity in a quick test, but a mere 30-50Ω can skew a sensor input significantly enough to place its signal out of the "normal" range to the point where the PCM does not accept it and sets a DTC. The scanner may show data for the sensor, but it would be wrong. That's generally when the mechanic picks up the wrench and starts changing parts, and the technician sets down the wrench and engages the brain.

Look again at the typical resistance range of a GM temperature sensor, and note the small differences which can result in substantial variation in interpretation by the PCM. There is a difference of less than 100Ω between normal operating temperature and overheat.

http://www.wwdsltd.com/files/CTS-MAT.gif

I am having the same issue with my 2016 Yukon slt. All fans began running (temp gauge at zero, fans ran when vehicle was turned off and continued to run when restarted) at almost 100,000 miles. I replaced the coolent temp sensor and it seemed to have fixed the problem for a couple months. The problem began again so I bought another temp sensor from the dealership. The problem seemed to be fixed for another month or so. Problem started again so I replaced the connector plug as I thought it could have a fitment issue. The problem went away for a couple weeks and it’s back. I am basically disconnecting the battery and resetting at this point and am unsure what to do now.

Welcome Aboard!

Having been on both sides of this situation, I believe it is relevant to remind everyone that intermittent issues are nearly impossible to diagnose unless and until the condition becomes more consistent. While scans and history data stored in the PCM can provide clues, it only indicates what the system has seen and not necessarily its cause.

For example, if an alternator begins to fail and either generates low voltage or applies some AC into the system ground, the PCM will record either low inputs on various sensors, or intermittent/high signals on various sensors. That doesn't mean that all those sensors are failing, since the root cause has absolutely nothing to do with any of them. The same applies to poor connections.

A recent example of that which I had was a Dodge Dakota with numerous and random error codes, accompanied by wandering idle and poor running, barely able to move the vehicle. The FIRST action was to pull the connectors at the PCM and clean corrosion and oxidation. After that, pulling the PCM history and monitoring real-time data made it apparent that a common problem was affecting everything from the TPS and MAP to the O²s and CTS. A little study of the diagrams revealed some potential suspects.

The eventual realization was that the main (upstream) oxygen sensor was randomly getting signals completely out of range. Removing the sensor and bench testing revealed that the 12V sensor heater was bleeding voltage to the sensor element, and that was pulling up the 5V reference supply at the PCM so that all sensors connected to that part of the circuit were getting indiscriminately skewed completely out of range. The owner had already replaced the MAP, two TPS sensors, the CTS, a fuel pressure regulator, and hesitated replacing the MAF and injectors on just a guess because of the high cost of the parts. One new O² solved it all.

In the case of the CTS on GMs, the PCM gets its signal not only from the variable resistor screwed into the water jacket, but through the wiring to and from the sensor, through the connections and splices hidden within the wire harness, through the PCM connectors, relies on the PCM 5V reference supply to be consistent, and requires that components are securely grounded to the chassis AND engine. One poor ground connection at the back of the head and all the sensors could look awry.

It looks to me to be a voltage issue, I recorded the temp gauge showing 0 and the fan running then took it onto the fwy and gunned it. As the V went up it crossed over 14V and the fan shut off and the temp gauge started working again. I had already replaced the temp sensor, that is clearly not the issue.

GM was telling me the thermostat was stuck open but if I disconnect the battery the fan stops and the gauge reads temp. This used to correct the problem for about a month or so.

Lately, it's happening more frequently.

Same issue here as well. My 2015 Yukon has been doing this off and on for over a year. I have noticed tho that it seems to happen when I adjust the thermostat knob or turn off the AC. Could it be loose pin grip in the climate controls or just a faulty ac controls? Ive only replaced the cts once and like everyone else it worked at first then 2 weeks later the issue came back. very frustrating

So after reading all these comments it seems I'm not the only one having this issue. At this point I am tired of this and how horribly bad these sensors are. We have replaced ours 3 times the last one just a week ago and here we are again with the fan blowing and my battery dying. My check engine light turned on and it takes about a day for it to go back to normal again. Gm needs to do something about these issues because we have kids and literally our only reliable car which won't be so reliable soon. If anyone has any more updates please update because I'm so over this issue. I have 113,000 miles on my 15 yukon and at 100,000 I already had to replace my transmission. This is totsl bs!

Just figured I'd add my .02 to this as I have a '15 Yukon and have experienced intermittent zero temperature readings with radiator fan running for the past few months. I ordered a new coolant temperature sensor (AC Delco for those keeping score), and replaced it myself. Ran with no issue for two weeks until this morning when I noticed the temperature was reading zero on my way to work and rolled my window down to hear the all too familiar sound of the fan whirring away.
When I got to my office I did some searching and landed on this thread. One thing that stuck out to me is those who have mentioned a voltage issue, and that getting that voltage up might factor in somehow. I distinctly recall a time in the past month or so that my radiator fan had been running and I was getting zero temp readings when I was driving my kids to school that I accelerated quickly after a traffic light and within 10-15 seconds the issue went away. That experience just stuck out for some reason because it seemed to me like the accelerating had led to the issue resolving in that case. Could the voltage be increased enough from an acceleration to lead to the problem resolving (at least temporarily)?
In any case, when I left work for lunch today, I intently accelerated a couple of times wondering if anything would come of it, and sure enough the issue resolved almost immediately.
What else could contribute to voltage issues? Bad alternator? Bad battery?

I replaced my thermostat and it has fixed the issue!!!

My issue with 0 reading started happening everyday….I replaced the thermostat a month ago and it hasn’t happened since