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Home >> Chevrolet >> 2020 >> Malibu LS >> Repair and Diagnosis >> External Pages >> Different car >> Section 119 (Active Noise Cancellation System) >> Diagnostic Information and Procedures >> DTC B126F, B1277, B127C, or B127D (IOR) >> Circuit/System Testing

Circuit/System Testing

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  1. Ignition/Vehicle & All vehicle systems - Off
  2. Disconnect the appropriate electrical connector: @ B77 Radio Volume Compensator Interior Noise Microphone
  3. Ignition - On / Vehicle - In Service Mode
  4. Test for 8 to 10 V between the test points:Signal circuit terminal 2 & Ground
    • If less than 8 V 
    1. Ignition/Vehicle & All vehicle systems - Off
    2. Disconnect the electrical connector:X2 @ A11 Radio
    3. Test for infinite resistance between the test points:Signal circuit terminal 2 & Ground
      • If less than infinite resistance - Repair the short to ground on the circuit.
      • Go to next step: If infinite resistance
    4. Test for less than 2 ohms between the test points:Signal circuit terminal 2 & The other end of the circuit
      • If 2 ohms or greater - Repair the open/high resistance in the circuit.
      • If less than 2 ohms - Replace the component:A11 Radio
    • If greater than 10 V 
    1. Ignition/Vehicle & All vehicle systems - Off
    2. Disconnect the electrical connector:X2 @ A11 Radio
    3. Ignition - On / Vehicle - In Service Mode
    4. Test for less than 1 V between the test points:Signal circuit terminal 2 & Ground
      • If 1 V or greater - Repair the short to voltage on the circuit.
      • If less than 1 V - Replace the component:A11 Radio
    • Go to next step: If between 8 and 10 V 
  5. Test for less than 1 V between the test points:Low Reference circuit terminal 1 & Ground
    • If greater than 1 V 
    1. Ignition/Vehicle & All vehicle systems - Off
    2. Disconnect the electrical connector:X2 @ A11 Radio
    3. Ignition - On / Vehicle - In Service Mode
    4. Test for less than 1 V between the test points:Low Reference circuit terminal 1 & Ground
    5. If 1 V or greater - Repair the short to voltage on the circuit.
    6. If less than 1 V - Replace the component:A11 Radio
    • Go to next step: If less than 1 V 
  6. Ignition/Vehicle & All vehicle systems - Off
  7. Disconnect the electrical connector:X2 @ A11 Radio
  8. Test for infinite resistance between the test points:Low Reference circuit terminal 1 & Ground
    • If less than infinite resistance 

      Repair the short to ground on the circuit.

    • Go to next step: If infinite resistance 
  9. Test for less than 2 ohms between the test points:Low Reference circuit terminal 1 & The other end of the circuit
    • If 2 ohms or greater 

      Repair the open/high resistance in the circuit.

    • Go to next step: If less than 2 ohms 

      Go to next step: Replace the appropriate component:B77 Radio Volume Compensator Interior Noise Microphone

  10. Ignition - On / Vehicle - In Service Mode
  11. Verify that no DTC listed in the DTC Descriptor Category is set.
    • If a related DTC is set 

      Replace the component:A11 Radio

    • Go to next step: If a DTC was not set 
  12. All OK.
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