[TheKrieg]

2003 4.3 Sonoma Hello everyone, so this p0128 code just came up. Three months ago, the thermostat was replaced with a Duralast Gold, which opens at 180 °F (15118DLG).I'm not sure if the thermostat opens too soon. On normal driving in 50-60ish degree weather, the temperature on the truck is normally around 170°F to 175°F.(It was 57°F outside while I was driving, so I'm not sure if this is normal for these trucks or if it's stuck on.) If anyone could help, it would be greatly appreciated. If you have any questions that I did not address, please let me know and I will respond

 

[Life is a Enigma]

So there's only two ways to get rid of the P128 pay somebody that has HP tuners to disable it or put back in the stock195 thermostat.

 

[TheKrieg]

So there's only two ways to get rid of the P128 pay somebody that has HP tuners to disable it or put back in the stock195 thermostat.

Ill go back to a 195 thermostat. But just wanted to make sure it was for sure going to be that thank you.

 

[Life is a Enigma]

Ill go back to a 195 thermostat. But just wanted to make sure it was for sure going to be that thank you.

There's a formula built into the ECM programming that's the engine needs to be at a certain temperature in a certain amount of time. If it doesn't reach that temperature in that time, it will set the P128. Unfortunately there is no way to change that formula. Only disable the p0128 with HP tuners or run the factory 195° thermostat.

 

[oldeerslayer]

I'd add that if you disable the code and run it colder than it's designed to be run you won't be operating the engine at peak efficiency which will likely result in poorer fuel mileage and performance, and increase pollution. Depending on where you are that could be an issue if you have inspections or if you care at all about the air you breathe.

 

[TheKrieg]

Thank ya'll for the help im going to start getting the 195 thermostat,i dont want to risk anything and hopefully it'll be good through out winter aswell.