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Home >> Chevrolet >> 2021 >> Blazer RS, FWD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 10 (Engine Controls And Fuel - 2.0L (LSY) - Diagnostic Information And Procedures (1 Of 2)) >> Diagnostic Information and Procedures >> DTC P0128 or P01F0 >> Circuit/System Verification

Circuit/System Verification

WARNING: This page is about a different variant/trim than selected.
  1. Verify the condition does not exist: Incorrect fluid level or condition - Refer to: Loss of Coolant (LSY)
    • 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
    • Go to next step: If a related DTC is not set 
  3. Perform the scan tool control function: Engine Block Coolant Valve Position = The parameter changes as commanded with the scan tool.
    • If the value does not change 

      Test or replace the component: Q97 Engine Coolant Flow Control Valve

    • Go to next step: If the value changes 
  4. Engine - Running @ 1800 to 2200 RPM

    Verify the scan tool parameter: ECT Sensor = Greater than 80°C (176°F) - Within 15 min

    • If 80°C (176°F) or colder 

      Test or replace the component: Q97 Engine Coolant Flow Control Valve

    • Go to next step: If warmer 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.

    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.
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