Circuit/System Testing

Vehicle OFF, disconnect the X1 harness connector at the A11 Radio and the X2 harness connector at the K73 Telematics Communication Interface Control Module, vehicle in Service Mode.
Test for less than 1 V between the signal circuit terminals listed below and ground:
- K73 Telematics Communication Interface Control Module signal circuit terminal 1 X2
- K73 Telematics Communication Interface Control Module signal circuit terminal 2 X2
- If 1 V or greater
  Repair the short to voltage on the circuit.
- If less than 1 V
Vehicle OFF.
Test for infinite resistance between the signal circuits listed below and ground:
- K73 Telematics Communication Interface Control Module signal circuit terminal 1 X2
- K73 Telematics Communication Interface Control Module signal circuit terminal 2 X2
- If less than infinite resistance
  Repair the short to ground on the circuit.
- If infinite resistance
Test for less than 2 Ω between the signal circuit terminals listed below:
- K73 Telematics Communication Interface Control Module signal circuit terminal 1 X2 and the A11 Radio signal circuit terminal 20 X1
- K73 Telematics Communication Interface Control Module signal circuit terminal 2 X2 and the A11 Radio signal circuit terminal 6 X1
- If 2 Ω or greater
  Repair the open/high resistance in the circuit.
- If less than 2 Ω
Replace the K73 Telematics Communication Interface Control Module.
Verify that the Connecting to OnStar® message is heard clearly through the audio system when the OnStar® blue button is pressed.
- If audio is not heard clearly
  Replace the A11 Radio.
- If audio is heard clearly
All OK.