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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 >> Component Testing

Component 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.
    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.
    IMPORTANT: You must perform the Circuit/System Verification first.
  1. Ignition OFF, disable the high voltage at the drive motor generator battery. Refer to High Voltage Disabling .
  2. Remove the drive motor generator battery upper cover. Refer to Drive Motor Battery Case Upper Cover, Front Cover, and Right Side Cover Replacement .
  3. Disconnect the inline harness connector at the HV positive contactor relay, and the inline harness connector at the HV negative and positive contactor relay.
  4. With a DMM measure between 20-30 ohms between terminals 1 and 2 at the connector on the component harness side at each contactor relay.
    • If the values are not within the specified range, replace the applicable HV relay contactor.
  5. Disconnect inline connectors X1 and X2 at the precharge relay.
  6. With a DMM measure between 55-75 ohms between terminals 5 and 6 at the precharge relay.
    • If the value is not within the specified range, replace the precharge contactor relay.
  7. Test for infinite resistance across the between the HV+ and HV- terminals on the HV positive contactor relay.
    • If the resistance is less than infinite, replace the HV positive contactor relay.
  8. Test for infinite resistance across the between the HV+ and HV- terminals on the HV negative contactor relay.
    • If the resistance is less than infinite, replace the HV negative contactor relay.
  9. Test for infinite resistance across the between the HV+ and HV- terminals on the HV precharge contactor relay.
    • If the resistance is less than infinite, replace the HV precharge contactor relay.
  10. Test for 11-13 ohms between X4 at the 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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