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Home >> Infiniti >> 2021 >> QX80 Premium Select, AWD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System (DTCS) (1 Of 5) >> Engine (ECM) >> DTC P0128: Thermostat Function >> DTC Diagnosis Procedure

DTC Diagnosis Procedure

NOTE: Never refuel before and during the following procedure.
  1. CHECK DTC PRIORITY 

    If DTC P0128 is displayed with DTC P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307 or P0308, first perform the trouble diagnosis for P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307 or P0308.

    Is applicable DTC detected?

    YES

    Perform diagnosis of applicable. Refer to DTC Index .

    NO

    GO TO 2.

  2. CHECK ENGINE COOLANT TEMPERATURE SENSOR 

    Check the engine coolant temperature sensor. Refer to Component Inspection .

    Is the inspection result normal?

    YES

    GO TO 3.

    NO

    Replace engine coolant temperature sensor. Refer to MULTI-WAY CONTROL VALVE : Exploded View .

  3. CHECK THERMOSTAT 

    Check the thermostat. Refer to MULTI-WAY CONTROL VALVE : Removal & Installation .

    Is the inspection result normal?

    YES

    INSPECTION END

    NO

    Replace thermostat.

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