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Home >> Cadillac >> 2007 >> Escalade EXT >> Repair and Diagnosis >> External Pages >> Different car >> Section 1038 (Cellular System, Entertainment System, And Navigation System) >> Diagnostic Information and Procedures >> OnStar Microphone Inoperative - Caller Cannot Be Heard >> Circuit/System Testing
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Circuit/System Testing

WARNING: This page is about a different car, the 2008 GMC Sierra, 2008 GMC Cab & Chassis Sierra, 2008 Chevrolet Silverado, and 2008 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, disconnect the harness connector at the cellular microphone.
  2. Ignition OFF, disconnect the harness connector at the inside rearview mirror.
  3. Ignition ON, test for 9.5-10.5 volts between the signal circuit terminal B and ground.
    • If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the CIM.
    • If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the CIM.
  4. Test for test for 9.5-10.5 volts between the signal circuit terminal B and the drain circuit terminal A.
    • If less than the specified range, test the drain circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the CIM.
  5. If all circuits test normal, replace the cellular microphone.
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