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Home >> GMC >> 2018 >> Acadia SL >> Repair and Diagnosis >> External Pages >> Different car >> Section 331 (Cellular System, Entertainment System, And Navigation System) >> Diagnostic Information and Procedures >> DTC B1277: Microphone 1 Input Signal Circuit (IO5/IO6) >> Circuit/System Testing
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Circuit/System Testing

WARNING: This page is about a different car, the 2017 GMC Acadia. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, disconnect the harness connector at the B24 Cellular Phone Microphone. Ignition On/Vehicle in Service Mode.
  2. Test for 9-11 V between the signal circuit terminal B and ground.
    • If less than 9 V 
    1. Ignition OFF, disconnect the X1 harness connector at the K74 Human Machine Interface Control 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.
      • 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 K74 Human Machine Interface Control Module.
    • If greater than 11 V 
    1. Ignition OFF, disconnect the X1 harness connector at the K74 Human Machine Interface Control Module. Ignition On/Vehicle in Service Mode.
    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.
      • If less than 1 V, replace the K74 Human Machine Interface Control Module.
    • If between 9-11 V 
  3. Test for less than 1 V between the signal circuit terminal A and ground.
    • If greater than 1 V 
    1. Ignition OFF, X1 harness connector at the K74 Human Machine Interface Control Module. Ignition On/Vehicle in Service Mode.
    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 K74 Human Machine Interface Control Module.
    • If less than 1 V 
  4. Ignition OFF, disconnect the X1 harness connector at the K74 Human Machine Interface Control Module.
  5. Test for infinite resistance between the B24 Cellular Phone Microphone signal circuit terminal A and ground.
    • If less than infinite resistance 

      Repair the short to ground in the circuit

    • 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

    • If less than 2 Ω 
  7. Replace the B24 Cellular Phone Microphone.
  8. Ignition On/Vehicle in Service Mode.
  9. Verify the DTC does NOT set.
    • If the DTC sets 

      Replace the K74 Human Machine Interface Control Module

    • If the DTC does not set 
  10. All OK.
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