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Home >> Hummer >> 2008 >> H2 4D Utility Wagon >> Repair and Diagnosis >> External Pages >> Different car >> Section 180 (Hybrid Energy Storage System) >> Diagnostic Information and Procedures >> DTC P0C77 or P1A20 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2008 GMC Yukon and 2008 Chevrolet Tahoe. However, it is still accessible from the selected car via links, so may be relevant.
IMPORTANT: You must perform the Circuit/System Verification first.
  1. Verify if DTCs P0C76, P0AC1, or P1A07 are set.
    • If DTCs P0C76, P0AC1, or P1A07 are set, diagnose them first.
  2. Verify if any HPCM DTCs are set.
    • If any HPCM DTCs are set, diagnose them first.
    3. WARNING: Before working on any high voltage system, be sure to wear the following Personal Protection Equipment:
    • Safety glasses with appropriate side shields when within 50 feet of the vehicle, either indoors or outdoors
    • Certified and up-to-date Class "0" Insulation gloves rated at 1000V with leather protectors
      • Visually and functionally inspect the gloves before use.
      • Wear the Insulation gloves at all times when working with the high voltage battery assembly, whether the system is energized or not.

    Failure to follow the procedure exactly as written may result in serious injury or death.
    WARNING: Always perform the High Voltage Disabling procedure prior to servicing any High Voltage component or connection. Personal Protection Equipment (PPE) and proper procedures must be followed.
    The High Voltage Disabling procedure will perform the following tasks:
    • Identify how to disable high voltage.
    • Identify how to test for the presence of high voltage.
    • Identify condition under which high voltage is always present and personal protection equipment (PPE) and proper procedures must be followed.

    Failure to follow the procedures exactly as written may result in serious injury or death.
  3. Connect the EL-48458  at the drive motor generator control module. Refer to the EL-48458  installation procedure located in High Voltage System Diagnosis (EL-48458) .
  4. Ignition ON, precharge the HV system by moving the HV contactor relay switch on the tester to the closed position. Verify that the Hi-voltage circuit LED for Hi-voltage greater than 60 volts illuminates and stays illuminated.
  5. Ignition OFF, disable the high voltage at the drive motor generator battery. Refer to High Voltage Disabling .
  6. Remove the drive motor generator battery upper cover. Refer to Drive Motor Battery Case Upper Cover, Front Cover, and Right Side Cover Replacement .
  7. Inspect and test the HV DC cables and connection points from the hybrid battery positive and negative output terminals to the HV positive and HV negative contactor relays.
    • If an open/high resistance condition is found on the HV cables or connection points, replace the faulty component.
  8. Inspect and test the HV DC cables and connection points from the HV positive, HV negative, and precharge contactor relays to the output HV DC terminals of the drive motor generator battery modules for an open/high resistance condition.
    • If an open/high resistance condition is found on the HV cables or connection points, replace the faulty component.
  9. Inspect and test the HV 300 volt positive and negative DC cables and connection points between the drive motor generator battery and the drive motor generator power inverter module (PIM) assembly for an open/high resistance condition.
    • If an open/high resistance condition is found on the HV cables or connection points, replace the drive motor battery 300 volt positive and negative cable.
  10. Connect the 12 volt battery.
  11. Install the HV manual disconnect lever.
  12. Ignition ON, engine OFF, connect a DMM between HV+ and HV- terminals of the HV positive contactor relay. Command the HV positive relay CLOSED. Verify less than 0.5 ohm.
    • If the resistance is greater than the specified value, replace the HV positive contactor relay.
  13. Connect a DMM between HV+ and HV- terminals of the HV negative relay. With a scan tool, command the HV negative relay CLOSED. Verify less than 0.5 ohm.
  14. Disconnect the X1 inline connector at the HV negative contactor relay.
  15. Test for infinite resistance across the HV+ and HV- terminal connections.
    • If less than the specified value, replace the HV negative contactor relay.
  16. Test for less than 1 ohm at the HV negative contactor relay inline harness connector terminal 2 and ground.
    • If the resistance is more than the specified value, repair the open/high resistance condition.
  17. Connect a test lamp between the HV negative contactor relay inline harness connector X1 terminal 1 and ground. The test lamp should not illuminate.
    • If the test lamp illuminates, test the control circuit for a short to voltage. If the circuit test normal, replace the drive motor generator battery control module.
  18. Command the HV negative relay CLOSED, with a scan tool. The test lamp should illuminate.
    • If the test lamp does not illuminate, test the control circuit for a short to ground, or an open/high resistance. If the control circuit tests normal, replace the drive motor generator battery control module.
  19. Disconnect the inline connector X1 at the HV positive contactor relay.
  20. Test for infinite resistance across the HV+ and HV- terminal connections.
    • If less than the specified value, replace the HV positive contactor relay.
  21. Test for less than 1 ohm at the HV positive contactor relay inline harness connector X1 terminal 2 and ground.
    • If the resistance is more than the specified value, repair the open/high resistance condition.
  22. Connect a test lamp between the HV positive contactor relay inline harness connector X1 terminal 1 and ground. The test lamp should not illuminate.
    • If the test lamp illuminates, test the control circuit for a short to voltage. If the circuit test normal, replace the drive motor generator battery control module.
  23. Connect a test lamp between HV positive contactor relay inline harness connector X1 terminal 1 and ground. Command the HV positive relay ON, with scan tool. The test lamp should illuminate.
    • If the test lamp does not illuminate, test the control circuit for a short to ground, or an open/high resistance. If the control circuit tests normal, replace the drive motor generator battery control module.
  24. Disconnect the inline connector X2 at the current limit precharge contactor relay.
  25. Test for infinite resistance across the HV+ and HV- terminal connections.
    • If less than the specified value, replace the drive motor power inverter current limit relay.
  26. Test for less than 1 ohm at the current limit precharge contactor relay connector X2 and ground.
    • If the resistance is more than the specified value, repair the open/high resistance condition.
  27. Disconnect the inline connector X1 at the current limit precharge contactor relay.
  28. Connect a test lamp between X1 connector terminal 1 and ground. The test lamp should not illuminate.
    • If the test lamp illuminates, test the control circuit for a short to voltage. If the circuit test normal, replace the drive motor generator battery control module.
  29. Command the current limit precharge contactor relay CLOSED, with scan tool. The test lamp should illuminate.
    • If the test lamp does not illuminate, test the control circuit for a short to ground, or an open/high resistance. If the control circuit tests normal, replace the drive motor generator battery control module.
  30. Test for 11-13 ohms between X4 at the current limit precharge contactor relay and the HV- terminal at the positive contactor relay.
    • If the value is not within the specified range, replace the HV precharge contactor current limiting resistor.
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