• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
• Review Strategy Based Diagnosis for an overview of the diagnostic approach.
• Diagnostic Procedure Instructions provides an overview of each diagnostic category.

The OnStar® button assembly consists of 3 buttons: Call/Answer, OnStar® Call Center, and OnStar® Emergency. The telematics communication interface control module supplies the OnStar® button assembly with 10 V via the 10 V reference circuit . Each of the buttons, when pressed, completes the circuit across a resistor allowing a specific voltage to be returned to the telematics communication interface control module over the keypad signal circuit. Depending upon the voltage range returned, the telematics communication interface control module is able to identify which button has been pressed.

• Vehicle in Service Mode/Ignition ON.
• Battery voltage must be between 9–16 V.

The telematics communication interface control module detects an open/high resistance on the keypad supply voltage circuit.

The telematics communication interface control module detects a valid signal on the keypad signal circuit for longer than 15 s. If one of the OnStar® buttons is held or stuck for 15 s or greater, the telematics communication interface control module will set this DTC.

• The OnStar® status LED turns red.
• No calls can be placed.
• The telematics communication interface control module will ignore all inputs from the OnStar® button assembly.

• The condition responsible for setting the DTC no longer exists.
• A history DTC will clear once 50 consecutive malfunction-free ignition cycles have occurred.

After any repair is made to the 10 V reference circuit or button signal circuit the fuse to the telematics communication interface control module must be removed for 30 s to reset the control module. Failure to do so could result in incorrect diagnosis.

OnStar/Telematics Schematics

Master Electrical Component List

OnStar Description and Operation

• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs

Control Module References for scan tool information

1. Vehicle OFF/Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the A98 Front Overhead Console Assembly. It may take up to 2 min for all vehicle systems to power down.
2. Test for less than 10 Ω between the ground circuit terminal 5 and ground.
• If 10 Ω or greater
1. Vehicle OFF/Ignition OFF.
2. Test for less than 2 Ω in the ground circuit end to end.
• If 2 Ω or greater, repair the open/high resistance in the circuit.
• If less than 2 Ω, repair the open/high resistance in the ground connection.
• If less than 10 Ω
3. Vehicle in Service Mode/Ignition ON.
4. Test for 8.0–10.5 V between the 10 V reference circuit terminal 16 and ground.
• If less than 8.0 V
1. Vehicle OFF/Ignition OFF, disconnect the harness connector at the K73 Telematics Communication Interface Control Module.
2. Test for infinite resistance between the 10 V reference circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance
3. Test for less than 2 Ω in the 10 V reference circuit end to end.
• 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.
• If greater than 10.5 V
1. Vehicle OFF/Ignition OFF, disconnect the harness connector at the K73 Telematics Communication Interface Control Module, vehicle in Service Mode/Ignition ON.
2. Test for less than 1 V between the 10 V reference 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
5. Vehicle OFF/Ignition OFF.
6. Test for 500–900 Ω between the signal circuit terminal 17 and ground.
• If less than 500 Ω
1. Disconnect the X1 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 on the circuit.
• If infinite resistance, replace the K73 Telematics Communication Interface Control Module.
• If greater than 900 Ω
1. Disconnect the X1 harness connector at the K73 Telematics Communication Interface Control Module, vehicle in Service Mode/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
3. Vehicle OFF.
4. 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 K73 Telematics Communication Interface Control Module.
• If between 500–900 Ω
7. Test or replace the A98 Front Overhead Console Assembly.

Perform the Diagnostic Repair Verification after completing the repair.

• Roof Console Replacement
• Control Module References for telematics communication interface control module replacement, programming and setup.