OnStar One or More Buttons Inoperative

OnStar One or More Buttons Inoperative

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.



Diagnostic Fault Information






Circuit/System Description

The OnStar(R) button assembly located on the inside rearview mirror consists of 3 buttons, Call/Answer, OnStar(R) Call Center, and OnStar(R) Emergency. The communication interface module (CIM) supplies the OnStar(R) button assembly with 10 volts via the keypad supply voltage circuit . Each of the buttons, when pressed, completes the circuit across a resister allowing a specific voltage to be returned to the CIM over the keypad signal circuit. Depending upon the voltage range returned, the CIM is able to identify which button has been activated.


Reference Information
Schematic Reference

OnStar Schematics (OnStar Schematics)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

OnStar Description and Operation (OnStar Description and Operation)
Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information


Circuit/System Testing

Important: Contact the OnStar(R) Call Center first before pressing the emergency button in order to notify them of the test.



1. Ignition OFF, disconnect the harness connector at the inside rearview mirror.
2. Ignition OFF, doors closed, interior lamps OFF, test for less than 5 ohms between the inside rearview mirror ground circuit terminal 8 and ground.

• If greater than specified range, test the ground circuit for an open/high resistance.

3. Ignition ON, test for 9.5-10.5 volts between the keypad supply voltage circuit terminal 12 and ground.

• If less than specified range, test the voltage supply circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the CIM.


• If greater than specified range, test the voltage supply circuit for a short to voltage. If the circuit tests normal, replace the CIM.

4. Test for less than 1 volt between the keypad signal circuit terminal 11 ground.

• If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the CIM.

5. Test for 9.5-10.5 volts between the keypad supply voltage circuit terminal 12 and the keypad signal circuit terminal 11.

• If not within the specified range, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the CIM.

6. Ignition OFF, disconnect the X1 harness connector at the CIM.
7. Ignition OFF, test for infinite resistance between the keypad signal circuit terminal 11 and ground.

• If less than the specified value, test the signal circuit for a short to ground.

8. If all circuits test normal, replace the inside rearview mirror.



Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Inside Rearview Mirror Replacement (Inside Rearview Mirror Replacement)
* Control Module References (Programming and Relearning) for CIM replacement, setup, and programming