DTC Descriptor
DTC B2476: Cellular Phone Select Service Switch
Circuit/System 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 resister 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
| • | The ignition must be in the RUN or ACC position. |
| • | The system voltage is at least 9.5 volts and no more than 15.5 volts. |
| • | All the above conditions are present for greater than 300 ms. |
Conditions for Setting the DTC
| • | The keypad signal circuit voltage to the VCIM is less than 2.8 volts or more than 3.2 volts. |
| • | The above conditions are present for greater than 300 ms. |
Action Taken When the DTC Sets
| • | The VCIM will ignore all inputs from the OnStar® button assembly. |
| • | No calls can be placed. |
| • | The OnStar® status LED turns RED. |
Conditions for Clearing the DTC
| • | The keypad signal circuit voltage is between 2.8 volts and 3.2 volts. |
| • | A history DTC clears after 50 malfunction free ignition cycles. |
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
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 supply voltage circuit terminal 12 and ground.
| ⇒ | If less than the specified range, test the voltage circuit for a short to ground or an open-high resistance. If the circuit tests normal, test or replace the inside rearview mirror. |
| ⇒ | If greater than the specified range, test the voltage circuit for a short to voltage. If the circuit tests normal, test or replace the inside rearview mirror. |
- Ignition OFF, Connect the harness connector at the inside rearview mirror.
- Disconnect the harness connector C1 at the VCIM.
- Ignition ON, verify a test lamp does not illuminate between the signal circuit terminal 11 and ground.
| ⇒ | If the test lamp illuminates, test the signal circuit for a short to voltage. |
- Verify a test lamp does not illuminate between the signal circuit terminal 11 and B+.
| ⇒ | If the test lamp illuminates, test the signal circuit for a short to ground. |
- Test for 1.3-1.7 ohm of resistance between the signal circuit terminal 11 and the supply voltage circuit terminal 6 while pressing the Call button.
| ⇒ | If not within the specified range, test the signal circuit for an open/high resistance. If the circuit tests normal, test or replace the inside rearview mirror. |
- Test for 2.8-3.2 ohm of resistance between the signal circuit terminal 11 and the supply voltage circuit terminal 6 while pressing the OnStar button.
| ⇒ | If not within the specified range, test the signal circuit for an open/high resistance. If the circuit tests normal, test or replace the inside rearview mirror. |
- Test for 12.8-13.2 ohm of resistance between the signal circuit terminal 11 and the supply voltage circuit terminal 6 while pressing the Emergency button.
| ⇒ | If not within the specified range, test the signal circuit for an open/high resistance. If the circuit tests normal, test or replace the inside rearview mirror. |
- If all circuits test normal, test or replace the VCIM.
Repair Instructions
