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

[dorlow]

Originally Posted by aleekat

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?

[aleekat]

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

[dorlow]

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.

[Stealthee]

Originally Posted by dorlow

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.

[dorlow]

Originally Posted by Stealthee

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.

[Stealthee]

How many miles were on the original?

[dorlow]

Originally Posted by Stealthee

How many miles were on the original?

About 100,000 miles.

[Stealthee]

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.

[Blue Bowtie]

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.

[dorlow]

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.

[Stealthee]

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.

[teetime1025]

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!

[dorlow]

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.

[Stealthee]

The failing sensor didn't kill your battery.

[dorlow]

Originally Posted by Stealthee

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.