P0128 still happening after thermostat and engine coolant temp sensor changed

[Mike_P]

P0128 still happening after thermostat and engine coolant temp sensor changed. Any other ideas?

 

[Atcer2018]

P0128 still happening after thermostat and engine coolant temp sensor changed. Any other ideas?

What temp thermostat are you running? P0128 is coolant below thermostat regulating temperature. Almost always the thermostat, low coolant level or a problem with the cooling fan. Sometimes new thermostats are bad out of the box. Did you test the new one in hot water before installation? Does your fan run all the time? Did you bleed the air out of the system after the thermostat install? Running a thermostat that is too low for the system emissions programming will set P0128 as the computers are set to see a minimum temperature and a colder running thermostat doesn’t allow the coolant to get hot enough.