I am new to this site...actually just having coolant readout problems on my 2007 cobalt...it goes blank --- and then comes back with a readout after some driving...distance varies...also at times engine lite comes on but does reset when coolant readout comes back.ll

 

Next time it goes blank. Check it with a scan tool and check the coolant temp. If it reads correctly on the scan tool. Replace your Thermostat. It's happened before. People say change Thermostat and sensor. But if the sensor works why replace it?

 

I would replace the coolant temp sensor, which is on the top of the engine , right where the top coolant hose goes . Just wait till engine has cooled down completely , unless you want hot coolant on your face , like me

 

And post in the "problems" section so people won't start bothering u around lol

 

I actually just got this problem yesterday, was going to replace the thermostat.

P0128 Engine Coolant Temperature (ECT) Below Thermostat Regulating Temperature ECM, PCM

 

Does ur temp do the same ?

 

Yeah, it showed ---* until this morning when I went to work, the temperature started working again, but the CEL was still on

 

But are the temps high or lower than usual?

 

thanks for the info....I am not a mechanic...so not even sure what a scan tool is...and certainly do not have one...I can only head to the garage for help...right now the care runs fine whether the read out is blank or not. So with 147000 miles I am ok as long as it keeps running.

 

Replace the sensor . You don't want this to keep happening . Your engine might cook someday if you don't watch the temps.

 

My temps are lower than normal, it's not even close to over heating

But they're at 160-180 range

 

I would do the tstat first then the sensor

 

What r the temps while driving

 

The temp shows --- when the car does not reach operating temps. It could take a few days for it then to throw a code.

I had this happen to me for a solid week. But I have a bluetooth adapter and a app on my phone and I monitored temps. Normal operating temps are 83*C (yes I'm Canadian).... On a 30 minute drive to work in traffic and highway. Temps never went higher then 60*C. But the dash still showed ---. it started showing later and it read fine. then a month later it happened again. I had it warrantied and they replaced the Tstat as the old one had "A large tear".

So replace the sensor if you want. But for sure replace the Tstat.

GM designed the car to go ---. I'm not sure why they did. maybe to make people worry and take it to a dealer quick. But either way it does that when the car doesn't reach operating temps.


(Also.... If the sensor was dead it would throw a code right away and it wouldn't be a thermostat performance related code)