An update.... must have parked too close to the Trailblazer, or it wasn't wearing it's mask... Got the P0128 error code on the Trailblazer last night. I hate cold weather!!

 

This nasty snow band won’t stop!! It’s piling up on the driveway!

 

Same snow/cold here. Clear a path and do it again tomorrow! Red is in a shop anyway getting tranny pulled I think to replace a fuel something that tells transmission to shift. I’m not a mechanic and his explanation is complete jibber! 🤔

 

Temp high is supposed to hit 28 tomorrow, with upper 30's this coming week. Maybe the pipes will thaw out... They say it is supposed to snow, but sounds more like rain. What a January for Minnesota. Normally we have a few weeks of temps in the below zero range, followed by snow in February. We shall see...
Temp right now is 8 degrees...

 

Hello I’ve had them same problem but I have replaced both the sensor and the thermostat and I still get —-F any other reason why this would happen

 

Need to reset error code with OBDII scanner and they should start working again.

 

Or just do a battery disconnect/reconnect. That clears any codes like the P0128.

 

P0128 clears itself.
The reason for P0128 is that the coolant temp does not reach 180F fast enough.
Is the coolant level full. Check under the pressure cap.
ACDelco 131-158 t-stat? Expensive but lasts forever, without problems.

 

Question, you installed the correct thermostat like Donbrew posted?
you burped the coolant?

https://www.chevyhhr.net/forums/how-...-system-60614/

As mentioned the code should clear by itself.

 

Adding my experience on the coolant thermostat and sensor .... The radiator petdick was easy to access. Here's how: get the front end up high enough to clear your belly. From the front slide under the passenger side and easily see the white coolant overflow jug with orange coolant. Feel 3 inches below that and you can easily get your fingers on your petdick.

On my 2008 Panel 2.4 litre 38000 km, the temperature was not going above 80°C so I suspected the t'stat but got fooled by the zero display on the gages and foolishly changed the sensor. After changing the 30 CAD thermostat, the gage temperature does climb to 88. Testing the bad original thermostat I found it began to open at 70. The rubber seal was good and I have used only DexCOOL.