[TJay74]

Originally Posted by TatsuSensei

Just had to order a coolant sensor as noone in Georgia has it in stock. Will replace and hopefully it will be this simple. Same symptoms. No reading and full blast fans.

Have you changed out the thermostat by chance?

While the coolant gauge in the cluster is dumbed down some on what it shows, the coolant temps you can read from the OBD2 port are live and 100% accurate.

There are a couple of fail safes that will cause the ECM to kill the gauge and run the fans. If it trips code P0128 from a stuck open thermostat or from someone putting a lower opening point stat than the OEM 192° thermostat and they didnt tune out the P0128 code it will kill the gauge and turn the fans on.

A bad coolant temp sensor that the ECM relies on will cause it to go into fail safe as well.

If you can get your hands on a BT dongle then you can use the Torque App to read the engine sensors and see what the actual sensor reading is and or the codes that are stored. The P0128 code doesnt trip the light until I think the 3rd reported malfunction.

[TatsuSensei]

Originally Posted by TJay74

Have you changed out the thermostat by chance?

While the coolant gauge in the cluster is dumbed down some on what it shows, the coolant temps you can read from the OBD2 port are live and 100% accurate.

There are a couple of fail safes that will cause the ECM to kill the gauge and run the fans. If it trips code P0128 from a stuck open thermostat or from someone putting a lower opening point stat than the OEM 192° thermostat and they didnt tune out the P0128 code it will kill the gauge and turn the fans on.

A bad coolant temp sensor that the ECM relies on will cause it to go into fail safe as well.

If you can get your hands on a BT dongle then you can use the Torque App to read the engine sensors and see what the actual sensor reading is and or the codes that are stored. The P0128 code doesnt trip the light until I think the 3rd reported malfunction.

Have not changed the Thermostat. It stopped working 2 weeks ago, then started working again like 12 hours later. Since there is a short of GM parts currently due to the strike, my dealer cannot get the part until <unknown>. I have a regular usb dongle for the ODB, I may take look into the BT version.

[TatsuSensei]

Originally Posted by TJay74

Have you changed out the thermostat by chance?

While the coolant gauge in the cluster is dumbed down some on what it shows, the coolant temps you can read from the OBD2 port are live and 100% accurate.

There are a couple of fail safes that will cause the ECM to kill the gauge and run the fans. If it trips code P0128 from a stuck open thermostat or from someone putting a lower opening point stat than the OEM 192° thermostat and they didnt tune out the P0128 code it will kill the gauge and turn the fans on.

A bad coolant temp sensor that the ECM relies on will cause it to go into fail safe as well.

If you can get your hands on a BT dongle then you can use the Torque App to read the engine sensors and see what the actual sensor reading is and or the codes that are stored. The P0128 code doesnt trip the light until I think the 3rd reported malfunction.

Ok ordered a BT dongle. It will be here tomorrow. Faster than the part.

[cellsafemode]

My car did the same thing after a rather jarring crappy road.

I have an x-431v device and it seems that once a code is thrown regarding the engine temp sensor, the car wont retest the sensor on next startup or even the 5th next startups. So it remains treated as dead and bad. You have to clear those codes (which dont result in a CEL, and dont show up on normal basic blue tooth code scanners) and then everything will magically work again unless there's a real problem with the sensor.

I've had no issues since then.

it's funny because the ecu will report and read the actual temp sensor data even while these codes are thrown and thus disabling the gauge clusters ....so if you do see the temp sensors showing realistic data, then it's just a matter of clearing the codes and the cluster should instantly wake up and start behaving (fan will turn off too).

I'm just not sure if torque (the free version at least) can see and clear those codes.

[TJay74]

Originally Posted by cellsafemode

My car did the same thing after a rather jarring crappy road.

I have an x-431v device and it seems that once a code is thrown regarding the engine temp sensor, the car wont retest the sensor on next startup or even the 5th next startups. So it remains treated as dead and bad. You have to clear those codes (which dont result in a CEL, and dont show up on normal basic blue tooth code scanners) and then everything will magically work again unless there's a real problem with the sensor.

I've had no issues since then.

it's funny because the ecu will report and read the actual temp sensor data even while these codes are thrown and thus disabling the gauge clusters ....so if you do see the temp sensors showing realistic data, then it's just a matter of clearing the codes and the cluster should instantly wake up and start behaving (fan will turn off too).

I'm just not sure if torque (the free version at least) can see and clear those codes.

Torque should be able to see the P0128 code, it is an engine code.

[cellsafemode]

Perhaps... Though the code for the coolant sensor doesn't activate cel, and I don't recall ever seeing torque see and clear codes that didn't also activate the check engine light. The clear codes function will skip many codes stored in the ecu, that is definite... Just not sure if this is one of them since I didn't try it this last time.

[meilmarc]

Mines did the same. Thermostat was stuck open. Switched and everything went back to normal.

[P-Nasty]

Old post but mine randomly does the same thing. In the worst case I didn’t know wat to do and after I shut off the car and let it sit for atleast an hour the fans decided to turn off. Now when it happens I just undo the battery and it will clear the problem until the next time. So I changed out the coolant temperature sensor today after the coolant reading was bottoming out and causing the fan to turn on high. So far it has cleared the issue, When I took off the old sensor it looked as if the coolant was starting to eat through it.

[Fernz]

I’m having the same issue , took it to dealer for fix under warranty . They said they replaced the sensor picked it up. Went for a drive the same day and bam ! Fan full blast ,coolant temp not reading . And the actual engine light turned on. Who knows if anything was even done to my car at the dealership.

[guitarman8373]

Just had mine do the same thing today after 5 years of ownership.

Randomly forced off my active rev match and put the radiator fan on full speed during a drive.

Ordered a new Thermostat Housing with all the new parts already in it. Should I also be looking at replacing the coolant temperature sensor as well?

[cellsafemode]

coolant sensor is fine. just replace the t-stat or take it out and fully clean it to remove the dexcool buildup that is causing it to be stuck open and reinstall

mechanically there is nothing really wrong with the thermostat... dexcool has coated the surfaces enough so that it no longer slides closed. replacing it is easier than cleaning the old one... I'd expect the next one to fail in 5 years again or sooner due to dexcool

[guitarman8373]

Originally Posted by cellsafemode

coolant sensor is fine. just replace the t-stat or take it out and fully clean it to remove the dexcool buildup that is causing it to be stuck open and reinstall

mechanically there is nothing really wrong with the thermostat... dexcool has coated the surfaces enough so that it no longer slides closed. replacing it is easier than cleaning the old one... I'd expect the next one to fail in 5 years again or sooner due to dexcool

Thanks!

[ctrlz]

Originally Posted by cellsafemode

coolant sensor is fine. just replace the t-stat or take it out and fully clean it to remove the dexcool buildup that is causing it to be stuck open and reinstall

What is the best way to clean this?

I have not heard of this. I wonder if it is from using tap water added to dexcool. Could be a salt precipitating on the back side of the 'stat. Maybe vinegar to clean it?

[nosugarboba]

It's your thermostat. Replaced mine with on on Amazon and all the issues went away.