after chenging the thrrmostat this cod p0128 comes back two same at oncewhat is goin on ?

Question

p0128 comes back even after changing the thermostat

Answer 1

Does the car overheat? is the new thermostat opening? after you drive the car for a few miles you can turn off the car and check to see if both radiator hoses are hot. If the one from the thermostat is not hot than the new thermostat might not be opening. 

you may have a faulty engine coolant temperature sensor