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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 >> DTC P0480, P0481, or P0482 (with HP2) >> Circuit/System Testing

Circuit/System Testing

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  1. Ignition OFF, open the hood to disable the Auto-Stop function.
  2. Ignition ON, verify the scan tool hood position parameter displays Open.
  3. Ignition OFF, disconnect all 5 cooling fan relays.
  4. Ignition ON, verify that a test lamp illuminates between ground and the ignition circuit terminal of each relay listed below:
    • FAN LO Relay terminal 85
    • FAN MID 1 Relay terminal 85
    • FAN CNTRL Relay terminal 86
    • FAN MID 2 Relay terminal 86
    • FAN HI Relay terminal 86
    • If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ignition circuit fuse is open, test all the components connected to the ignition voltage circuit and replace as necessary.
  5. Set the DMM on the diode setting. Connect the black lead to ground. Connect the red lead of the DMM to a control circuit terminal listed below:
    • FAN LO Relay terminal 86
    • FAN MID 1 Relay terminal 86
    • FAN CNTRL Relay terminal 85
    • FAN MID 2 Relay terminal 85
    • FAN HI Relay terminal 85

      The DMM should display OL.

    • If less than the specified range, test the appropriate relay coil control circuit for a short to ground. If the circuit tests normal, replace the K20 ECM.
  6. Command the appropriate cooling fan relay ON and OFF with a scan tool. The DMM should transition from OL when commanded OFF to less than 1 V when commanded ON.
    • If the circuit voltage does not correspond to the specified values, test the control circuit for an open/high resistance or for a short to voltage. If the circuit tests normal, replace the K20 ECM.
  7. If all circuits test normal, test or replace the appropriate KR20 relay.
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