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Home >> Toyota >> 2008 >> FJ Cruiser RWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 238 (Engine Control System (1NZ-FE)) >> SFI System >> DTC P0128 Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature) >> Inspection Procedure

Inspection Procedure

WARNING: This page is about a different car, the 2008 Toyota Yaris. However, it is still accessible from the selected car via links, so may be relevant.

HINT:

Read freeze frame data using a Techstream. Freeze frame data record the engine condition when malfunctions are detected. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, if the air-fuel ratio was lean or rich, and other data, from the time the malfunction occurred.

  1. CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P0128) 
    1. Connect a Techstream to the DLC3.
    2. Turn the ignition switch to ON.
    3. Turn the tester ON.
    4. Select the following menu items: Powertrain / Engine and ECT / Trouble Codes.
    5. Read DTCs.

      Result 

      RESULT CHART

      Display (DTC Output) Proceed To
      P0128 A
      P0128 and other DTCs B

      HINT:

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

    B: GO TO DTC CHART (See  DIAGNOSTIC TROUBLE CODE CHART   ) 

    A: Go to next step 

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

    NG: REPAIR OR REPLACE COOLING SYSTEM 

    OK: Go to next step 

  3. INSPECT THERMOSTAT 
    1. Remove the thermostat (See REMOVAL ).
    2. Check the valve opening temperature of the thermostat.

      Standard: 

      80°C to 84°C (176°F to 183°F) 

      HINT:

      In addition to the above check, confirm that the valve is completely closed when the temperature is below the standard.

    3. Reinstall the thermostat (See INSTALLATION ).

    NG: REPLACE THERMOSTAT  (See REMOVAL )

    OK: Go to next step 

  4. REPLACE ENGINE COOLANT TEMPERATURE SENSOR 
  5. CHECK WHETHER DTC OUTPUT RECURS (DTC P0128) 
    1. Connect a Techstream to the DLC3.
    2. Turn the ignition switch to ON.
    3. Turn the tester ON.
    4. Clear DTCs.
    5. Turn the ignition switch to OFF and cool the engine down until the engine coolant temperature and the intake air temperature are the same.
    6. Start the engine and warm it up.
    7. On the tester, select the following menu items: Powertrain / Engine and ECT / Trouble Codes / Pending Code.
    8. Read pending DTCs.

      Result 

      RESULT CHART

      Display (DTC Output) Proceed To
      P0128 A
      No pending DTC output B

    B: END 

    A: REPLACE ECM (See  REMOVAL   ) 

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