Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Circuit/System Testing
- Ignition OFF and vehicle systems OFF, disconnect the harness connector X1 at the A11 radio and disconnect the harness connector X2 at the K73 telematics communication interface control module, ignition ON.
- Test for less than 1 V between the K73 telematics communication interface control module signal circuit terminal 1 and ground
- If 1 V or greater
Repair the short to voltage on the circuit.
- If less than 1 V
- If 1 V or greater
- Test for less than 1 V between the K73 telematics communication interface control module low reference circuit terminal 2 and ground.
- If 1 V or greater
Repair the short to voltage on the circuit.
- If less than 1 V
- If 1 V or greater
- Ignition OFF.
- Test for infinite resistance between the K73 telematics communication interface control module signal circuit terminal 1 and ground
- If less than infinite resistance
Repair the short to ground on the circuit.
- If infinite resistance
- If less than infinite resistance
- Test for infinite resistance between the K73 telematics communication interface control module low reference circuit terminal 2 and ground.
- If less than infinite resistance
Repair the short to ground on the circuit.
- If infinite resistance
- If less than infinite resistance
- Test for less than 2 Ω between the K73 telematics communication interface control module signal circuit terminal 1 and the A11 radio cellular telephone voice low reference circuit terminal 20.
- If 2 Ω or greater
Repair the open/high resistance in the circuit.
- If less than 2 Ω
- If 2 Ω or greater
- Test for less than 2 Ω between the K73 telematics communication interface control module low reference circuit terminal 2 and the A11 radio low reference circuit terminal 6.
- If 2 Ω or greater
Repair the open/high resistance in the circuit.
- If less than 2 Ω
- If 2 Ω or greater
- 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
- If audio is not heard clearly
- All OK.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.