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

[Lbi2000]

Coolant Temperature Sensor. A very easy switch out and you won't lose much coolant at all if you clamp all the hoses going in/out of the waterpump next to it and the thermostat and do it when its cold. It sounds like the classic issue of the coolant temp sensor not giving any reading to ECM and the engine runs the fans high because it thinks it could be overheating and cannot tell. Good luck.

More... i replaced the temperature sensor *and* the thermostat .. they are both right there and a very easy cheap thing to do. while you are there u could also replace the water pump which is a nit on these vehicles.

 

[jaxscuby]

skipping record over here..

new to me 2016 Tahoe with 126K miles.
past monday..the fans came on while the "wife" was running the youngins around.
google search with the symptoms..replace coolant temperature seonsor..
replaces the ECT (engine coolant temperature sensor) with one from dealership..$58..
you know GM..so I bought GM sensor.

replaced the sensor the following morning..past tuesday..a whole 5 minutes..
fans behave normal..the gauge shows proper reading..

so now the Thanksgiving weekend..lo & behold..fans back at it..no check engine light.
same engine temperature reading from gauges..right at 160..

search results..the temp sensor..and/or the thermostat..
so search for replacement thermostat..and shows housing + thermostat..~$60..aftermarket..

So questions,

1. how often does a thermostat fail?

2. how often does ECT sensor fail?

why would I ask these questions when this just happen to me.

the aftermarket temp sensors ~$25..ok i will buy a few (3-4)..
the aftermarket thermostat housing/ thermostat..$60..a spare..

accustom to wrenching on my vehicles since the 80's..but my recently sold
2014 Equinox was almost trouble free..

 

[jaxscuby]

so replaced the thermostat & housing (can we find the thermostat by itself?).
only could find a 207 thermostat. will hunt for the factory after turkey weekend.
The fans did not come on. warmed to 210. Have gas up later today for a "test drive".

knock on wood.

 

[L8T BURB]

The issues here are definitely thermostat related. I had this precise issue with my 2015 Suburban. Replaced the coolant temperature sensor twice, problem would clear up a couple days each time before returning again.

Finally replaced the coolant temperature sensor AND the thermostat with GM genuine parts and problem totally solved. My theory is that the thermostat (both on 5.3 and 6.2 applications) becomes faulty and stays partially opened at all times, not allowing the coolant to reach full operating temps of 210. This seems to be an intermittent issue when the weather is very warm outside, but when ambient temps are below 50 degrees, there's no chance that a faulty thermostat thats partially stuck open will get you to 210. When the engine runs for an extended period and cannot get to 210, it will eventually go to "fail safe" mode, engaging the cooling fans non-stop including a few minutes after shut-off, not allowing the AC compressor to engage, coolant temp gauge will drop to zero, and if you run it long enough like this, you'll also get a CEL for a "coolant temp below threshold".

I have seen posts on this forum where people immediately start talking about wiring harnesses, ECM replacements, etc. So so costly repairs that do not solve the issue, but there's such little information out there with definitive results, which has made this issue so elusive to many. What should be a ~$100 repair, ends up being several hundred or thousands while the faulty thermostat was truly the root cause of it all.

Hope this helps!!