DTC Descriptors
DTC B2476 00: Cellular Phone Select Service Switch
Circuit Description
The OnStar® button assembly consists of three buttons, Call/Answer, OnStar® Call Center and OnStar® Emergency. Ten volts is supplied to the button assembly on 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 vehicle communication interface module (VCIM) on the keypad signal circuit. Depending upon the voltage range returned, the VCIM is able to identify which button has been pressed.
Conditions for Running the DTC
| • | Battery voltage must be between 9-16 volts. |
Conditions for Setting the DTC
The VCIM 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 VCIM will ignore all inputs from the OnStar® button assembly. |
| • | The OnStar® status LED turns RED. |
| • | No calls can be placed. |
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
OnStar Schematics
Connector End View Reference
Cellular Communication Connector End Views
Description and Operation
OnStar Description and Operation
Electrical Information Reference
Scan Tool Reference
Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the inside rearview mirror.
- Ignition ON, test for 9.8-10.2 volts between the keypad supply voltage circuit terminal 12 and ground.
| ⇒ | 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. |
- Test for 0 volt between the keypad signal circuit terminal 11 and ground.
| ⇒ | If greater than the specified range, test the keypad signal circuit for a short to voltage. If the circuit tests normal, replace the VCIM. |
- Test for 9.8-10.2 volts between the keypad supply voltage circuit terminal 12 and the keypad signal circuit terminal 11.
| ⇒ | If less than the specified range, test the keypad signal circuit for an open/high resistance. If the circuit tests normal, replace the VCIM. |
- Test for less than 5 ohms between the mirror ground circuit terminal 8 and ground.
| ⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
- Ignition OFF, disconnect the VCIM C1 connector. Test for infinite resistance between the keypad signal circuit terminal 11 and ground.
| ⇒ | If less than the specified range, test the keypad signal circuit for a short to ground. |
- If all circuits test normal, test or replace the button assembly.
Component Testing
- Ignition OFF, disconnect the harness connector at the inside rearview mirror .
- Test for infinite resistance between the keypad supply voltage terminal 12 and the keypad signal terminal 11.
| ⇒ | If less than the specified range, replace the inside rearview mirror. |
- Test for 1.4k-1.6k ohms between the keypad supply voltage terminal 12 and the keypad signal terminal 11 while pressing the black phone button.
| ⇒ | If not within the specified range, replace the inside rearview mirror. |
- Test for 2.7k-3.3k ohms between the keypad supply voltage terminal 12 and the keypad signal terminal 11 while pressing the blue On-Star® button.
| ⇒ | If not within the specified range, replace the inside rearview mirror. |
- Test for 11.7k-14.3k ohms between the keypad supply voltage terminal 12 and the keypad signal terminal 11 while pressing the red emergency button.
| ⇒ | If not within the specified range, replace the inside rearview mirror. |
Repair Instructions
