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Home >> Hummer >> 2008 >> H2 4D Utility Wagon >> Repair and Diagnosis >> External Pages >> Different car >> Section 512 (Engine Controls/Fuel - 5.3L, 6.0L, 6.2L - DTC P0010 To DTC P0358) >> Diagnostic Information and Procedures >> DTC P0128 >> Circuit/System Verification

Circuit/System Verification

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  1. Ignition OFF, inspect the cooling system surge tank for the proper coolant level. Refer to Cooling System Leak Testing , and Cooling System Draining and Filling (Static Fill) .
    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 .
  3. Ignition ON, observe the scan tool IAT Sensor and ECT Sensor parameters. The ECT, IAT, and ambient temperatures should be within 6°C (11°F) of each other.
  4. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
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