so I have an 09 cobalt ss/tc, ive had it for about 2 months, all i have put in it is a K&N drop.
I was driving home from Dallas and got a MIL light on. I went to my school, scaned it and got this.
P0128 Engine Coolant Temperature (ECT) Below Thermostat Regulating Temperature ECM, PCM

Im a little confused, i live in ****** texas, i dont understand whats going on? Maybe the sensor is stuck open and letting too much coolant flow? what could be triggering this? I dont really want to take it to the dealership if i can take care of this myself, im not in good standing with them since i wrote a horrible survey about them lol

any advise?

 

Check your thermostat. If it's in the same place as it is on the LSJ, good luck. It's a little bitch to get to.

 

Your either looking at a thermostate replacment oor the sensor is buggered.
But dont overlook a possible loose connector.