Mike's Workshop Manuals: Service manuals for every vehicle
Home >> Chevrolet >> 2020 >> Trax LS, AWD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls And Fuel - 1.8L (2H0) >> Diagnostic Information and Procedures >> DTC P0128 >> Circuit/System Verification

Circuit/System Verification

  1. Verify the condition does not exist: Incorrect fluid level or condition - Refer to Loss of Coolant
    • 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 component/system:
    • B34 Engine Coolant Temperature Sensor
    • {If equipped} B203 Radiator Coolant Temperature Sensor
    • {If equipped} E41 Engine Coolant Thermostat Heater
    • {If equipped} Q74 Engine Coolant Bypass Valve
    • Go to next step: If a related DTC is not set 
  3. Perform the scan tool control function: Engine Coolant Thermostat Heater and Cooling Fan
    1. Engine Coolant Thermostat Heater - 100%
    2. Cooling Fan - 90%
    3. Engine Speed - 1, 800 to 2, 200 RPM
    • Verify the scan tool parameter: ECT Sensor = Less than 85°C (185°F) - Within 5 min
    • If 85°C (185°F) or warmer 

      Refer to Circuit/System Testing

    • Go to next step: If colder than 85°C (185°F) 
  4. Perform the scan tool control function: Engine Coolant Thermostat Heater and Cooling Fan
    1. Engine Coolant Thermostat Heater - 0%
    2. Cooling Fan - 0%
    3. Engine Speed - 1, 800 to 2, 200 RPM
    • Verify the scan tool parameter: ECT Sensor = Greater than 102°C (215°F) - Within 5 min
    • If 102°C (215°F) or colder 

      Test or replace the component: E41 Engine Coolant Thermostat Heater

    • Go to next step: If warmer than 102°C (215°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.

    Verify the DTC does not set.

    • If the DTC sets 

      Refer to: Circuit/System Testing

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