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Home >> Cadillac >> 2018 >> Escalade Base, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 5 (Engine Controls And Fuel - 6.0L (L96) - DTC P0010 To DTC P0341) >> Diagnostic Information And Procedures >> DTC P0128: Engine Coolant Temperature (ECT) Below Thermostat Regulating Temperature >> Circuit/System Verification

Circuit/System Verification

WARNING: This page is about a different car, the 2018 Chevrolet Suburban 3500 HD. However, it is still accessible from the selected car via links, so may be relevant.
  1. Verify the condition does not exist: Incorrect fluid level or condition - Refer to Loss of Coolant (L96)
    • If a condition exists 

      Repair or replace as necessary.

    • Go to next step: If no condition exists 
  2. Verify there are no DTCs set related to the following system/component:
    • B34 Engine Coolant Temperature Sensor
    • {If equipped} B203 Radiator Coolant Temperature Sensor
    • {If equipped} Q74 Engine Coolant Bypass Valve
    • Go to next step: If a related DTC is not set 
  3. Perform the following test for the appropriate component. - Engine Coolant Thermostat
    1. Engine Run Time - Greater than 10 min
    2. Increase the engine speed slowly to 3000 RPM.
    3. Air Conditioning - Off
    • Verify the scan tool parameter: ECT Sensor = Greater than 85°C (185°F) - Within 5 min
    • If 85°C (185°F) or colder 

      Test or replace the component: Engine Coolant Thermostat

    • Go to next step: If warmer than 85°C (185°F) 
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

    Verify the DTC does not set.

    • If the DTC sets 

      Refer to Circuit/System Testing below

    • Go to next step: If the DTC does not set 
  5. All OK.
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