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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.
    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.
  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 case upper cover, front cover, and right side cover. Refer to Drive Motor Battery Case Upper Cover, Front Cover, and Right Side Cover Replacement .
  3. Ignition OFF, connect the 12 volt battery.
  4. Disconnect the harness connector at the battery vent fan motor.
  5. Connect a test lamp between the ignition circuit terminal 2 and ground.
  6. Ignition ON, command the battery pack vent fan speed to 60 percent. The test lamp should illuminate after a 5-7 second delay.
    • If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.
  7. Verify a test lamp illuminates between B+ and the ground circuit terminal 3.
    • If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
  8. Ignition OFF, connect the harness connector at the battery vent fan motor.
  9. Disconnect X2 harness connector at the BECM.
  10. Verify a test lamp illuminates between the vent fan relay control circuit terminal 7 and ground.
    • If the test lamp does not illuminate, test the control circuit for an open/high resistance. If the circuit tests normal, replace the generator battery vent fan relay.
  11. Connect a 3A fused jumper wire between the vent fan motor relay control circuit terminal 7 and ground.
  12. Ignition ON, test for 4.8-5.2 volts between the signal circuit terminal 2 and ground.
    • If the voltage is not within the specified range, test the signal circuit for a short to voltage, short to ground, or an open/high resistance. If the circuit tests normal, replace the generator battery vent fan.
  13. If all circuits test normal, replace the drive motor generator battery control module.
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