LEMON Manuals: Even more car manuals for everyone
Home >> GMC >> 2021 >> Terrain SLT, 4WD >> Repair and Diagnosis (Single Page) >> Accessories & Equipment >> Accessories Control Systems >> Active Noise Cancellation System >> Diagnostic Information and Procedures >> DTC B126F, B1277, B127C, or B127D (Amplifier) >> Circuit/System Testing

Circuit/System Testing

  1. Ignition OFF, disconnect the harness connector at the appropriate B77 Radio Volume Compensator Interior Noise Microphone. Ignition ON.
  2. Test for 7.8 - 8.8 V between the signal circuit terminal 2 and ground.
    • If less than 7.8 V 
    1. Ignition OFF, disconnect the X3 harness connector at the T3 Audio Amplifier / K108 Active Noise Cancellation Module.
    2. Test for infinite resistance between the signal circuit and ground.
      • If less than infinite resistance, repair the short to ground in the circuit.
      • Go to next step: If infinite resistance
    3. Test for less than 2 Ω in the signal circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the T3 Audio Amplifier / K108 Active Noise Cancellation Module.
    • If greater than 8.8 V 
    1. Ignition OFF, disconnect the X3 harness connector at the T3 Audio Amplifier / K108 Active Noise Cancellation Module. Ignition ON.
    2. Test for less than 1 V between the signal circuit and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • Go to next step: If less than 1 V, replace the T3 Audio Amplifier / K108 Active Noise Cancellation Module.
    • Go to next step: If between 7.8 - 8.8 V 
  3. Test for less than 1 V between the signal circuit terminal 1 and ground.
    • If greater than 1 V 
    1. Ignition OFF, X3 harness connector at the T3 Audio Amplifier / K108 Active Noise Cancellation Module. Ignition ON.
    2. Test for less than 1 V between the signal circuit and ground.
      • If 1 V or greater, repair the short to voltage in the circuit.
      • If less than 1 V, replace the T3 Audio Amplifier / K108 Active Noise Cancellation Module.
    • Go to next step: If less than 1 V 
  4. Ignition OFF, disconnect the X3 harness connector at the T3 Audio Amplifier / K108 Active Noise Cancellation Module.
  5. Test for infinite resistance between the B77 Radio Volume Compensator Interior Noise Microphone signal circuit terminal 1 and ground.
    • If less than infinite resistance 

      Repair the short to ground in the circuit

    • Go to next step: If infinite resistance 
  6. Test for less than 2 Ω in the signal circuit end to end.
    • If 2 Ω or greater 

      Repair the open/high resistance in the circuit

    • Go to next step: If less than 2 Ω 
  7. Replace the B77 Radio Volume Compensator Interior Noise Microphone.
  8. Ignition ON
  9. Verify the DTC does NOT set.
    • If the DTC sets 

      Replace the T3 Audio Amplifier / K108 Active Noise Cancellation Module.

    • Go to next step: If the DTC does not set 
  10. All OK.
scientia non olet · About LEMON Manuals