DTC P0128: Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature): General Description

Thermostat, installed between engine and radiator, is automatically opened or closed in order to control the amount of flowing water so that ECM maintains engine coolant temperature at certain level. If, generally, engine coolant temperature reaches about 80°C (176 °F), wax in the thermostat is expended in order to open the valve. And, reversely, if coolant temperature is low, wax in the thermostat is contracted that makes valve is closed. Thermostat maintains engine temperature in order to active best engine performance and prevent overheat and over cooling.