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Home >> GMC >> 2006 >> Sierra 1500 HD, RWD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 25 (ENGINE CONTROLS - 6.6L - DIAGNOSIS (DTCs P0016-P0401)) >> DTC P0128 >> Circuit/System Verification

Circuit/System Verification

WARNING: This page is about a different variant/trim than selected.
  1. If the ignition has been OFF for 10 hours or more, the ECT and the IAT should be within 6°C (11°F) of each other and also the ambient temperature. Turn ON the ignition with the engine OFF and use a scan tool to observe the IAT and the ECT sensor parameters.
  2. Inspect the ECT sensor terminals for corrosion and for engine coolant leaking through the sensor.
  3. Use the scan tool to verify the proper operation of the engine cooling fans.
  4. Turn OFF the ignition.
  5. Inspect the cooling system surge tank for the proper engine coolant level. Refer to Cooling System Leak Testing and Draining and Filling Cooling System (w/RPO HP2) or Draining and Filling Cooling System (w/o RPO HP2) .
  6. Verify the proper heat range and the operation of the thermostat. Refer to Thermostat Diagnosis .
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