Code PO128 Coolant Thermostat Performance

[Supermoto68]

I keep having this code pop up over and over, does it have to do with my tuner ? Any help would be appreciated

 

[2004LB7]

Does your engine seem to be running cool or taking a while to come up to temp?

More then likely it is bad thermostats or temp sensor

 

[ikeG]

If you Google it, people have copy pasted the diagnostic instructions into a reply on other forums.
If you find the thermostats are good and ect sensor is accurate, you end up testing circuits. Any resistance will make the sensor report a lower temp than actual, which the ecm sets p0128 for.

Sent from my SM-G960U1 using Tapatalk

 

[Supermoto68]

Does your engine seem to be running cool or taking a while to come up to temp?

More then likely it is bad thermostats or temp sensor

I have been watching my temp in my truck an it seems to be running around 185 degrees all the time. Is this below normal as my truck keeps setting off this sensor every few days.

 

[Ron Nielson]

Lots of reading material here: https://www.dtcdecode.com/Chevrolet/P0128.