General Information

P0128 Coolant Thermostat (Coolant Temperature below Thermostat Regulating Temperature)

General Information

Component Location





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. The Thermostat maintains engine temperature to achieve the best engine performance plus prevent overheat and overcooling.

DTC Description

Checking time and coolant temperature under detecting condition, if the coolant temperature dose not reach the target temperature as the test timer reaches the threshold time, ECM sets P0128.

DTC Detecting Condition