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. |
DTC Descriptors
DTC B2476: Cellular Phone Select Service SwitchDiagnostic 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 | -- | -- |
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 communication interface module (CIM) supplies the OnStar® button assembly with 10 volts via the keypad supply voltage circuit. Each of the buttons, when pressed, completes the circuit across a resistor 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.
Conditions for Running the DTC
| • | Ignition ON. |
| • | Battery voltage must be between 9-16 volts. |
Conditions for Setting the DTC
The CIM detects a short to voltage, short to ground, or an open/high resistance on the keypad supply voltage circuit.
Action Taken When the DTC Sets
| • | The OnStar® status LED turns red. |
| • | No calls can be placed. |
| • | The CIM will ignore all inputs from the OnStar® button assembly. |
Conditions for Clearing the DTC
| • | The condition responsible for setting the DTC no longer exists. |
| • | A history DTC will clear once 100 consecutive malfunction-free ignition cycles have occurred. |
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 Testing
- Ignition OFF, disconnect the harness connector at the onstar switch.
- Test for less than 5 Ω between the ground circuit terminal 5 and ground.
- Ignition ON, test for less than 1 V between the keypad signal circuit terminal 2 and ground.
- Ignition OFF, test for 600 K - 700 K Ω between the keypad signal circuit terminal 2 and ground.
- Ignition ON, test for 9.8-10.2 V between the keypad supply voltage circuit terminal 4 and ground.
- If all circuits test normal, test or replace the onstar switch.
| ⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
| ⇒ | If greater than the specified range, test the keypad signal circuit for a short to voltage. If the circuit tests normal, replace the CIM. |
| ⇒ | If less than the specified range, test the keypad signal circuit for a short to ground. If the circuit tests normal, replace the CIM. |
| ⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. If the circuit tests normal, replace the CIM. |
| ⇒ | 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 CIM. |
| ⇒ | If greater than the specified range, test the supply voltage circuit for a short to voltage. If the circuit tests normal, replace the CIM. |
Component Testing
- Ignition OFF, disconnect the harness connector at the onstar switch.
- Test for infinite resistance between the keypad supply voltage terminal 4 and the keypad signal terminal 3.
- Test for 1.4 K - 1.6 K Ω between the keypad supply voltage terminal 4 and the keypad signal terminal 3 while pressing the black phone button.
- Test for 2.7 K - 3.3 K Ω between the keypad supply voltage terminal 4 and the keypad signal terminal 3 while pressing the blue On-Star® button.
- Test for 2.7 K - 3.3 K Ω between the keypad supply voltage terminal 4 and the keypad signal terminal 3 while pressing the red emergency button.
| ⇒ | If less than the specified range, replace the onstar switch. |
| ⇒ | If not within the specified range, replace the inside onstar switch. |
| ⇒ | If not within the specified range, replace the inside onstar switch. |
| ⇒ | If not within the specified range, replace the onstar switch. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for CIM replacement, setup, and programming |
