2006 GMC Envoy Q&A

2006 GMC Envoy Question: i replaced the thermostat and i am still setting p0128 code.what next.

The scan tool i have will not read sensors or tell me anything other than the code that has been set. i don't want to go to a mechanic and would like to know the most likely problem causing this code. i am not the one driving the car and am not sure when and under what conditions the code is being set, i think it is happening after the car is warmed up and been driven a while. -
Answer 1
If you were able to read data, the temperature sensor needs to be monitored. And by the way, we are Technicians/Mechanics. -
Answer 2
Could also be that water temperature sensor is not working right. -
Comment 1
Just looking on a wiring diagram and was wondering where the water temp sensor is, all I see is a ECT for the computer, which also runs on the CAN line to the instrument cluster. Could you help me out, Please. -