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HOMESERVICE MANUALSHYUNDAI2011TUCSON GL, AUTOMATICREPAIR AND DIAGNOSISENGINE PERFORMANCETESTING & DIAGNOSISENGINE CONTROL SYSTEM DIAGNOSIS (1 OF 2)DTC P0128: COOLANT THERMOSTAT (COOLANT TEMPERATURE BELOW THERMOSTAT REGULATING TEMPERATURE)INSPECTION REPAIRSYSTEM INSPECTION
2011 Hyundai Tucson GL, Automatic

System Inspection

2011 Hyundai Tucson GL, AutomaticSECTION System Inspection
  1. Coolant Level Inspection
    1. Check the cooling system coolant level.
    2. Is the coolant in the reservoir at the proper level?

      YES 

      • Go to next step as below.

      NO 

  2. Thermostat Inspection
    1. Check if the thermostat bypass valve is stuck in the open position or if the correct type of thermostat was installed. Replace thermostat as necessary and go to VERIFICATION OF VEHICLE REPAIR .
    2. Check the valve opening temperature of the thermostat.

      Specification (Valve opening temperature):  80~84°C (176~183°F)

    3. If the opening temperature is not as specified, Replace thermostat as necessary and go to VERIFICATION OF VEHICLE REPAIR .

      If OK, go to next step as below.

  3. ECT Sensor Inspection
    1. Ignition "OFF".
    2. Disconnect ECTS connector.
    3. Measure resistance between terminals 1 and 3 of the sensor connector (Component side)

      Specification 

      SPECIFICATIONS

      Temp.(°C) Resistance (kΩ) Temp.(°C) Resistance (kΩ)
      -20 14.1 ~ 16.8 40 Approx. 1.2
      0 Approx. 5.8 60 Approx. 0.6
      20 2.3 ~ 2.6 80 Approx. 0.3
    4. Is resistance within the specification?

      YES 

      • Go to next step as below.

      NO 

      • Check ECTS for contamination, deterioration, or damage. Substitute with a known-good ECTS and check for proper operation. If the problem is corrected, replace ECTS and then go to VERIFICATION OF VEHICLE REPAIR .
RENDER: 1.0x

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.