DTC P0128: Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature) [08/2013 - ]: Description

WARNING: This page is about a different car, the 2014 Lexus ES 300h. However, it is still accessible from the selected car via links, so may be relevant.

HINT:

This DTC relates to the thermostat.

This DTC is stored when the engine coolant temperature does not reach 75°C (167°F) despite sufficient engine warm-up time having elapsed.

DTC No.	DTC Detection Condition	Trouble Area
P0128	All of the following conditions are met for 5 seconds (2 trip detection logic): (a) Cold start. (b) The engine is warmed up. (c) The engine coolant temperature is less than 75°C (167°F).	Thermostat Cooling system Engine coolant temperature sensor ECM