Diagnostic Instructions
| • | 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. |
Diagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Keypad Supply Voltage | B2476 | B2476 | B2476 | -- |
Keypad Green LED Signal | 1 | 1 | 2 | -- |
Keypad Red LED Signal | 1 | 1 | 2 | -- |
Keypad Signal | 3 | 3 | -- | B2482 |
Inside Rearview Mirror Ground | -- | 1 | -- | -- |
1. OnStar® LED Inoperative 2. LED Illuminated At All Times 3. OnStar® Buttons Inoperative | ||||
Circuit/System Description
The OnStar® button assembly consists of 3 buttons: Call/Answer, OnStar® Call Center, and OnStar® Emergency. The vehicle communication interface module (VCIM) supplies the OnStar® button assembly with 10 volts via the keypad 10 volt reference circuit. Each of the buttons, when pressed, completes the circuit across a resistor 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
Connector End View Reference
Description and Operation
OnStar Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
Important: Contact the OnStar® Call Center first before pressing the emergency button in order to notify them of the test.
Ignition ON, press the OnStar® Call buttons one at the time. Verify that all of the OnStar® buttons operate normally.
| ⇒ | If one or more, but not all, OnStar® buttons are inoperative, replace the inside rearview mirror. |
| ⇒ | If all of the OnStar® buttons are inoperative, refer to OnStar Button Circuit Malfunction. |
Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the inside rearview mirror.
- Test for less than 5 Ω between the mirror ground circuit terminal 8 and ground.
- Ignition ON, test for less than 1 volt between the keypad signal circuit terminal 11 and ground.
- Ignition OFF, test for 600 K - 700 K Ω between the keypad signal circuit terminal 11 and ground.
- Ignition ON, test for 9.8-10.2 V between the keypad supply voltage circuit terminal 12 and ground.
- If all circuits test normal, test or replace the inside rearview mirror.
| ⇒ | If greater than the specified range, test the circuit for an open/high resistance. |
| ⇒ | If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the VCIM. |
| ⇒ | If less than the specified range, test the signal circuit for a short to ground. If the circuit tests normal, replace the VCIM. |
| ⇒ | If greater than the specified range, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the VCIM. |
| ⇒ | If less than the specified range, test the supply voltage circuit for a short to ground or open/high resistance. If the circuit tests normal, replace the VCIM. |
| ⇒ | If greater than the specified range, test the supply voltage circuit for a short to voltage. If the circuit tests normal, replace the VCIM. |
Component Testing
- Ignition OFF, disconnect the harness connector at the inside rearview mirror.
- Test for infinite resistance between the supply voltage terminal 12 and the signal terminal 11.
- Test for 1.4k-1.6k ohms between the supply voltage terminal 12 and the signal terminal 11 while pressing the black Call/Answer button.
- Test for 2.7k-3.3k ohms between the supply voltage terminal 12 and the signal terminal 11 while pressing the blue On-Star® button.
- Test for 11.7k-14.3k ohms between the supply voltage terminal 12 and the signal terminal 11 while pressing the red emergency button.
| ⇒ | If not the specified value, replace the inside rearview mirror. |
| ⇒ | If not within the specified range, replace the inside rearview mirror. |
| ⇒ | If not within the specified range, replace the inside rearview mirror. |
| ⇒ | If not within the specified range, replace the inside rearview mirror. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for VCIM replacement, setup, and programming |
