Circuit/System Testing

Microphone Malfunction

1. Ignition OFF, disconnect the harness connector at the B24 Cellular Phone Microphone, ignition ON.
2. Test for 8.0-10.5 V between the signal circuit terminal B and ground.
   • If less than 8.0 V 
   1. Ignition OFF, disconnect the X2 harness connector at the K73 Telematics Communication 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 vehicle K73 Telematics Communication Interface Control Module.
   • If greater than 10.5 V 
   1. Ignition OFF, disconnect the X2 harness connector at the K73 Telematics Communication Interface Control 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.
      • If less than 1 V, replace the K73 Telematics Communication Interface Control Module.
   • If between 8.0-10.5 V 
3. Test for less than 1 V between the low signal circuit terminal A and ground.
   • If greater than 1 V 
   1. Ignition OFF, disconnect the X2 harness connector at the K73 Telematics Communication Interface Control 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, repair the K73 Telematics Communication Interface Control Module.
   • If less than 1 V 
4. Test for greater than 8 V between the signal circuit terminal B and the low signal circuit terminal A.
   • If less than 8 V 
   1. Ignition OFF, disconnect the X2 harness connector at the K73 Telematics Communication Interface Control Module.
   2. Test for infinite resistance between the low 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 low 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 vehicle K73 Telematics Communication Interface Control Module.
   • If greater than 9 V 
5. Test or replace the B24 Cellular Phone Microphone.

Cellular Telephone Voice Malfunction

1. Ignition OFF and vehicle systems OFF, disconnect the X2 harness connector at the K73 Telematics Communication Interface Control Module and the X1 harness connector at the K74 Human Machine Interface Control Module, ignition ON.
2. Test for less than 1 V between each signal circuit listed below and ground:
   • K73 Telematics Communication Interface Control Module signal circuit Terminal 6
   • K73 Telematics Communication Interface Control Module signal circuit Terminal 12
   • If greater than 1 V 

     Repair the short to voltage in the circuit.

   • If less than 1 V 
3. Ignition OFF.
4. Test for infinite resistance between the between each signal circuit listed below and ground:
   • K73 Telematics Communication Interface Control Module signal circuit Terminal 6
   • K73 Telematics Communication Interface Control Module signal circuit Terminal 12
   • If less than infinite resistance 

     Repair the short to ground on the circuit.

   • If infinite resistance 
5. Test for less than 2 Ω in between each signal circuit listed below end to end:
   • K73 Telematics Communication Interface Control Module signal circuit Terminal 6
   • K73 Telematics Communication Interface Control Module signal circuit Terminal 12
   • If 2 Ω or greater 

     Repair the open/high resistance in the circuit.

   • If less than 2 Ω 
6. Replace the K73 Telematics Communication Interface Control Module.
7. Verify that your voice is heard clearly by the OnStar Call Center after completing a blue button press.
   • If your voice can not be heard clearly 

     Replace the K74 Human Machine Interface Control Module.

   • If your voice can be heard clearly 
8. All OK.