DTC P0128: Thermostat [10/2015 - 03/2019]: Procedure

1. Connect the Techstream to the DLC3.
2. Turn the engine switch on (IG).
3. Turn the Techstream on.
4. Enter the following menus: Powertrain / Engine / Trouble Codes.
5. Read the DTCs.

   Powertrain > Engine > Trouble Codes 

   Result

   Result	Proceed to
   DTC P0128 is output	A
   DTC P0128 and other DTCs are output	B

   HINT: 

   If any DTCs other than P0128 are output, troubleshoot those DTCs first.

Result: 

B 

GO TO DTC CHART. Refer to  DIAGNOSTIC TROUBLE CODE CHART [10/2015 - 08/2016]  , or refer to  DIAGNOSTIC TROUBLE CODE CHART [08/2016 - 11/2017]  , or refer to  DIAGNOSTIC TROUBLE CODE CHART [11/2017 - 05/2018]  , or refer to  DIAGNOSTIC TROUBLE CODE CHART [05/2018 - 03/2019] 

Result: 

A 

See step  2

1. Check for defects in the cooling system that might cause the system to be too cold, such as abnormal cooling fan operation or any modifications.

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPAIR OR REPLACE COOLING SYSTEM 

Result: 

OK 

See step  3

1. Inspect the water inlet with thermostat sub-assembly (thermostat opening temperature).

   Refer to INSPECTION [09/2014 - ]

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPLACE WATER INLET WITH THERMOSTAT SUB-ASSEMBLY. Refer to  REMOVAL [09/2014 - ] 

Result: 

OK 

See step  4

1. Inspect the engine coolant temperature sensor.

   Refer to INSPECTION [09/2014 - ]

   HINT: 

   Perform "Inspection After Repair" after replacing the engine coolant temperature sensor.

   Refer to INITIALIZATION [09/2014 - ]

   Result

   Proceed to
   OK
   NG

Result: 

OK 

REPLACE ECM. Refer to  REMOVAL [09/2014 - ] 

Result: 

NG 

REPLACE ENGINE COOLANT TEMPERATURE SENSOR. Refer to  REMOVAL [09/2014 - ]