DTC P0128-00: Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature); DTC P0128-07: Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature) Mechanical Failure [02/2019 - 06/2020]: Description

WARNING: This page is about a different car, the 2020 Toyota RAV4 and 2019 Toyota RAV4. However, it is still accessible from the selected car via links, so may be relevant.

The ECM uses the engine coolant temperature sensor, installed to the water outlet, and the No. 2 engine coolant temperature sensor*1, installed to the radiator pipe assembly, to monitor the operation of the thermostat.

DTC No.	Detection Item	DTC Detection Condition	Trouble Area	MIL	Memory	Note
P0128-00	Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)	All of the following conditions are met for 5 seconds or more (2 trip detection logic): Cold start. The engine is warmed up. The engine coolant temperature is less than 75°C (167°F).	Water inlet with thermostat sub-assembly Engine cooling system Engine coolant temperature sensor ECM	Comes on	DTC stored	SAE Code: P0128
P0128-07	Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature) Mechanical Failure	All of the following conditions are met for 30 seconds or more (2 trip detection logic)1: Water inlet housing with water pump sub-assembly is operating, The engine coolant temperature is less than 75°C (167°F). The difference between the rate of change of the engine coolant temperature sensor and No. 2 engine coolant temperature sensor is within the threshold. The difference between the temperature detected by the engine coolant temperature sensor and that detected by the No. 2 engine coolant temperature sensor is within the threshold. All of the following conditions are met for 3 times (2 trip detection logic)2: The engine coolant temperature is less than 75°C (167°F). The value of the change in engine coolant temperature is less than the threshold.	Water inlet with thermostat sub-assembly Engine cooling system Engine coolant temperature sensor No. 2 engine coolant temperature sensor*1 ECM	Comes on	DTC stored	SAE Code: P0128

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

MIL

Memory

Note

P0128-00

Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)

All of the following conditions are met for 5 seconds or more (2 trip detection logic):

Cold start.
The engine is warmed up.
The engine coolant temperature is less than 75°C (167°F).

Water inlet with thermostat sub-assembly
Engine cooling system
Engine coolant temperature sensor
ECM

Comes on

DTC stored

SAE Code: P0128

P0128-07

Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature) Mechanical Failure

All of the following conditions are met for 30 seconds or more (2 trip detection logic)*1:

Water inlet housing with water pump sub-assembly is operating,
The engine coolant temperature is less than 75°C (167°F).
The difference between the rate of change of the engine coolant temperature sensor and No. 2 engine coolant temperature sensor is within the threshold.
The difference between the temperature detected by the engine coolant temperature sensor and that detected by the No. 2 engine coolant temperature sensor is within the threshold.

All of the following conditions are met for 3 times (2 trip detection logic)*2:

The engine coolant temperature is less than 75°C (167°F).
The value of the change in engine coolant temperature is less than the threshold.

Water inlet with thermostat sub-assembly
Engine cooling system
Engine coolant temperature sensor
No. 2 engine coolant temperature sensor*1
ECM

Comes on

DTC stored

SAE Code: P0128

*1: w/ Grille Shutter System
*2: w/o Grille Shutter System