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Home >> Cadillac >> 2009 >> STS V >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls And Fuel - 4.4L - DTC P0010 To DTC P0158 >> DTC P0128 >> Circuit/System Verification
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Circuit/System Verification

  1. Ignition OFF, inspect the cooling system surge tank for the proper coolant level. Refer to Cooling System Leak Testing (Charge Air Cooling) or Cooling System Leak Testing (Powertrain) and Cooling System Draining and Filling (GE 47716) or Cooling System Draining and Filling (Static Fill) .
  2. Ignition OFF for 8 hours or greater.
  3. Ignition ON, observe the scan tool IAT and ECT sensor parameters. The ECT, IAT, and ambient temperatures should be within 15°C (27°F) of each other.
  4. Use the scan tool to verify the proper operation of the engine cooling system fans.
  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. IMPORTANT: A critical analysis of the operation of the thermostat is necessary to properly diagnose these DTCs.
  6. Verify the proper heat range and the operation of the thermostat. Refer to Thermostat Diagnosis .
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