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Home >> Hummer >> 2008 >> H2 4D Utility Wagon >> Repair and Diagnosis >> External Pages >> Different car >> Section 98 (Engine Cooling System) >> Diagnostic Information and Procedures >> DTC P0480 or P0481 >> Circuit/System Testing

Circuit/System Testing

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P0480

  1. Ignition OFF, disconnect the cooling fan low relay from the underhood fuse block.
  2. Ignition ON, verify that a test lamp illuminates between the fan low relay coil voltage supply circuit and ground.
    • If the test lamp does not illuminate, test the fan low relay coil voltage supply circuit for and open/high resistance.
  3. Connect a test lamp between the fan low relay coil supply voltage circuit and the fan low relay coil control circuit. With a scan tool, command the fan relay 1 ON and OFF. Verify that the test lamp turns ON and OFF with each command.
    • If the test lamp remains illuminated with each command, test the relay coil control circuit for a short to ground. If the circuit tests normal, replace the control module.
    • If the test lamp does not illuminate, test the relay coil control circuit for and open or a short to voltage. If the circuit tests normal, replace the control module.
  4. If the circuits test normal, replace the fan low relay.

P0481

  1. Ignition OFF, disconnect the cooling fan high relay from the underhood fuse block.
  2. Ignition ON, verify that a test lamp illuminates between the fan high relay coil voltage supply circuit and ground.
    • If the test lamp does not illuminate, test the fan high relay coil voltage supply circuit for and open/high resistance.
  3. Connect a test lamp between the fan high relay coil supply voltage circuit and the fan high relay coil control circuit. With a scan tool, command the fan relays 2 and 3 ON and OFF. Verify that the test lamp turns ON and OFF with each command.
    • If the test lamp remains illuminated with each command, remove the fan control relay and retest. If the test lamp now turns ON and OFF with the fan control relay removed, replace the fan control relay. If the test lamp still remains illuminated when commanded ON and OFF, test the fan high relay coil control circuit for a short to ground. If the circuit tests normal, replace the control module.
    • If the test lamp does not illuminate, test the fan high relay coil control circuit for and open or a short to voltage. If the circuit tests normal, replace the control module.
  4. If all circuits test normal, replace the fan high relay.
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