OnStar Button LED Inoperative

OnStar Button LED 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 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 vehicle communication interface module (VCIM) 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 VCIM over the keypad signal circuit. Depending upon the voltage range returned, the VCIM 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 Verification

1. Ignition ON, command the Green LED ON and OFF with a scan tool while observing the green LED on the inside rearview mirror. The green LED should turn ON and OFF when commanded.
2. Command the red LED ON and OFF with a scan tool while observing the red LED on the inside rearview mirror. The red LED should turn ON and OFF when commanded.



Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the inside rearview mirror.
2. Ignition 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. Connect a test lamp between the inoperative LED signal circuit and the ground circuit terminal 8.
4. Command the appropriate LED ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

• If the test lamp is always ON, test the inoperative signal circuit for a short to voltage. If the circuit tests normal, replace the VCIM.


• If the test lamp is always OFF, test the inoperative signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the VCIM.

5. 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 VCIM replacement, setup, and programming