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Home >> Buick >> 2015 >> Regal GS, AWD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 15 (Engine Controls And Fuel - 2.4L - DTC P0114 To DTC P0604) >> 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. Ignition ON, verify that DTC P00B3, P00B6, P0101, P0102, P0103, P0111, P0112, P0113, P0116, P0117 or P0118 is not set.
    • If DTC P00B3, P00B6, P0101, P0102, P0103, P0111, P0112, P0113, P0116, P0117 or P0118 is not set 
  2. Verify the cooling system is filled to the correct coolant level. Refer to Cooling System Draining and Filling (GE 47716) , and Loss of Coolant .
    • If the coolant level is not correct 

      Repair as necessary

    • If the coolant level is correct 
  3. Engine running for 15 min with the A/C OFF, increase the engine speed to 3,000 RPM.
  4. Verify the scan tool ECT Sensor parameter is greater than 80°C (176°F) .
    • If less than 80°C (176°F) 

      Replace the Engine Coolant Thermostat.

    • If greater than 80°C (176°F) 
  5. 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.
  6. Verify the DTC does not set.
    • If the DTC sets 

      Refer to Circuit/System Testing.

    • If the DTC does not set 
  7. All OK.
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