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Home >> GMC >> 2018 >> Terrain Denali, FWD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 12 (Engine Controls And Fuel - 1.5L (LYX) - Diagnostic Information And Procedures (P0010 - P034B)) >> 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 variant/trim than selected.
  1. Verify the cooling system is filled to the correct coolant level. Refer to Cooling System Leak Testing , and Cooling System Draining and Filling (GE 47716)Cooling System Draining and Filling (Static) .
    • If the coolant level is not correct 

      Repair as necessary

    • Go to next step: If the coolant level is correct 
    2. NOTE:

    A critical analysis of the operation of the thermostat is necessary to properly diagnose this DTC.

  2. Verify the proper heat range and the operation of the thermostat. Refer to Thermostat Diagnosis .
    • If a condition is found 

      Replace the Thermostat.

    • Go to next step: If a condition is not found 
  3. 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.
  4. Verify the DTC does not set.
    • If the DTC sets 

      Refer to Step 1.

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