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

[Blue Bowtie]

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.

[Bperry1]

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.

[Blue Bowtie]

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.

[Cafe Y Tabaco]

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.

[Dirt71]

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 overit]

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!

[GDNenn]

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?

[Dirt71]

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

[Dirt71]

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