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 variant/trim than selected.

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