DTC P0128-00: Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature); DTC P0128-07: Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature) Mechanical Failure [09/2022 - ]: 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, 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): The engine is started cold and then warmed up. When the estimated engine coolant temperature is 75°C (167°F) or higher, the actual engine coolant temperature is less than 75°C (167°F).	Water inlet with thermostat sub-assembly (thermostat) Cooling system Engine coolant temperature sensor No. 2 engine coolant temperature sensor ECM	Comes on	DTC stored	SAE Code: P0128 DTC for Mexico Models: Does not apply
P0128-07	Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature) Mechanical Failure	for 2WD All of the following conditions are met for 30 seconds or more (2 trip detection logic): 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. for AWD All of the following conditions are met for 3 times (2 trip detection logic): 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 (thermostat) Cooling system Engine coolant temperature sensor No. 2 engine coolant temperature sensor*1 ECM	Comes on	DTC stored	SAE Code: P0128 DTC for Mexico Models: Does not apply

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):

The engine is started cold and then warmed up.
When the estimated engine coolant temperature is 75°C (167°F) or higher, the actual engine coolant temperature is less than 75°C (167°F).

Water inlet with thermostat sub-assembly (thermostat)
Cooling system
Engine coolant temperature sensor
No. 2 engine coolant temperature sensor
ECM

Comes on

DTC stored

SAE Code: P0128
DTC for Mexico Models: Does not apply

P0128-07

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

for 2WD

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,
2. The engine coolant temperature is less than 75°C (167°F).
3. The difference between the rate of change of the engine coolant temperature sensor and No. 2 engine coolant temperature sensor is within the threshold.
4. 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.

for AWD

All of the following conditions are met for 3 times (2 trip detection logic):
1. The engine coolant temperature is less than 75°C (167°F).
2. The value of the change in engine coolant temperature is less than the threshold.

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

Comes on

DTC stored

SAE Code: P0128
DTC for Mexico Models: Does not apply