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Home >> Hummer >> 2008 >> H2 4D Utility Wagon >> Repair and Diagnosis >> External Pages >> Different car >> Section 319 (Engine Cooling System) >> Diagnostic Information and Procedures >> Cooling Fan Inoperative (with HP2) >> Circuit/System Testing

Circuit/System Testing

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NOTE:

You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.

  1. Ignition OFF, open the hood to disable the Auto-Stop function. Refer to Hybrid Modes of Operation Description .
  2. Ignition ON, verify the scan tool hood position parameter displays Open.
  3. Ignition OFF, disconnect the cooling fan relays.
  4. Ignition ON, verify that a test lamp illuminates between the Fan Control relay ground circuit terminal 87 and B+.
    • If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
  5. Connect a 30 A fused jumper between the Fan Control relay switch circuit terminal 30 and the relay ground circuit terminal 87. This will complete the left side fan ground circuit. Leave this jumper in place for the remainder of this procedure.
    6. NOTE:

    The following test must be performed on the high, low, and both medium speed relay circuits.

  6. Ignition ON, verify that a test lamp illuminates between ground and the relay switched ignition circuit terminal listed below:
    • Fan Low Relay terminal 87
    • Fan Mid 1 Relay terminal 87
    • Fan Mid 2 Relay terminal 30
    • Fan High Relay terminal 30
    • If the test lamp does not illuminate, test the appropriate relay switch B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the relay switch B+ circuit fuse is open, test the relay controlled output circuit for a short to ground. If the circuit tests normal, test or replace the appropriate G10 cooling fan.
  7. Connect a 30 A fused jumper between the cooling fan relay circuit terminals listed below:
    • Fan High Relay terminals 87 and 30
    • Fan Low Relay terminals 87 and 30

      Verify the appropriate fan is activated.

    • If the corresponding cooling fan does not activate, test the relay controlled output circuit and the cooling fan ground circuit for an open/high resistance. If the circuits tests normal, test or replace the appropriate G10 cooling fan.
  8. Connect a 30 A fused jumper between the cooling fan relay circuit terminals listed below:
    • Fan Mid 1 Relay terminal 87 and 30
    • Fan Mid 2 Relay terminal 30 and 87

      The appropriate fan should activate and operate at a reduced speed.

    • If the corresponding cooling fan does not activate, test the relay controlled output circuit for an open/high resistance. If the circuit tests normal, test or replace the appropriate R10 cooling fan resistor.
    • If the corresponding cooling fan activates, replace the appropriate cooling fan relay.
  9. Ignition OFF, install the Fan Control relay.
  10. Ignition ON, connect a 30 A fused jumper wire between the Fan Low relay terminals 87 and 30. Both cooling fans should activate and operate at a low speed.
    • If both fans do not activate, test the Fan Control Relay switched output circuit terminal 87A for a short to ground or an open/high resistance. If the circuit tests normal, test or replace the Fan Control relay.
  11. If all the circuits test normal, test or replace the appropriate cooling fan relay.
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