DTC P0128-00: Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature); DTC P0128-07: Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature) Mechanical Failure [11/2021 - 03/2023]: Procedure

1. Read the DTCs.

   Powertrain > Engine > Trouble Codes 

   Result

   Result	Proceed to
   DTC P0128-00 or P0128-07 is output	A
   DTC P0128-00 or P0128-07 and other DTCs are output	B

   HINT: 

   If any DTCs other than P0128-00 or P0128-07 are output, troubleshoot those DTCs first.

Result: 

B 

GO TO DTC CHART. Refer to  DIAGNOSTIC TROUBLE CODE CHART [11/2021 - 03/2023] 

Result: 

A 

See step  2

1. Check for defects in the engine 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 ENGINE COOLING SYSTEM 

Result: 

OK 

See step  3

1. Inspect the engine coolant temperature sensor (for cylinder head side).

   Refer to INSPECTION [11/2021 - ]

   HINT: 

   Perform "Inspection After Repair" after replacing the engine coolant temperature sensor (for cylinder head side).

   Refer to INITIALIZATION [11/2021 - ]

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPLACE ENGINE COOLANT TEMPERATURE SENSOR (FOR CYLINDER HEAD SIDE). Refer to  REMOVAL [11/2021 - ] 

Result: 

OK 

See step  4

1. Inspect the engine coolant temperature sensor (for outlet side).

   Refer to INSPECTION [11/2021 - ]

   HINT: 

   Perform "Inspection After Repair" after replacing the engine coolant temperature sensor (for outlet side).

   Refer to INITIALIZATION [11/2021 - ]

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPLACE ENGINE COOLANT TEMPERATURE SENSOR (FOR OUTLET SIDE). Refer to  REMOVAL [11/2021 - ] 

Result: 

OK 

See step  5

1. Clear the DTCs.

   Powertrain > Engine > Clear DTCs 

2. Turn the ignition switch off and wait for at least 30 seconds.

   Result

   Proceed to
   NEXT

Result: 

NEXT 

See step  6

1. Drive the vehicle in accordance with the driving pattern described in Confirmation Driving Pattern.
2. Read the DTCs.

   Powertrain > Engine > Trouble Codes 

   Result

   Result	Proceed to
   DTCs are not output	A
   DTC P0128-00 or P0128-07 is output	B

Result: 

A 

CHECK FOR INTERMITTENT PROBLEMS. Refer to  CHECK FOR INTERMITTENT PROBLEMS [11/2021 - ] 

Result: 

B 

REPLACE WATER CONTROL VALVE. Refer to  REMOVAL [11/2021 - ]