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Home >> Hummer >> 2008 >> H2 4D Utility Wagon >> Repair and Diagnosis >> External Pages >> Different car >> Section 366 (Active Noise Cancellation System) >> Diagnostic Information and Procedures >> DTC B1277, B127C, or B127D >> Circuit/System Testing

Circuit/System Testing

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  1. Ignition OFF, disconnect the harness connector at the appropriate microphone.
  2. Ignition ON Radio ON , test for 0.47-2.75 V between the microphone (-) signal circuit terminal A and ground.
    • If greater than the specified range, test the circuit for a short to voltage. If the circuit tests normal, replace the amplifier.
    • If less than the specified range, test the circuit for an open/high resistance or a short to ground. If the circuit tests normal, replace the amplifier.
  3. Test for 5.75-8.03 V between the microphone (+) signal circuit terminal B and ground.
    • If greater than the specified range, test the circuit for a short to voltage. If the circuit tests normal, replace the amplifier.
    • If less than the specified range, test the circuit for an open/high resistance or a short to ground. If the circuit tests normal, replace the amplifier.
  4. If all circuits test normal, replace the appropriate microphone.
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