Diagnostic Instructions
DTC Descriptor
DTC B2476 00 : Cellular Phone Select Service Switch Malfunction
Circuit/System Description
The OnStar® button assembly consists of 3 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
| • | 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 milliseconds. |
Conditions for Setting the DTC
| • | The VCIM powers the button assembly through the keypad supply voltage circuit for 11.5 ms, turns the power OFF, then waits for 50 ms and sees a voltage value greater than 1.8 volts on this circuit. |
| • | The above conditions are present for greater than 300 milliseconds. |
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 VCIM powers the button assembly through the keypad supply voltage circuit for 11.5 ms, turns the power OFF, then waits for 50 ms and sees a voltage value less than 1.8 volts on this circuit. |
| • | A history DTC clears after 50 malfunction-free ignition cycles. |
Reference Information
Schematic Reference
OnStar Schematics
Connector End View Reference
Entertainment/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.
- Test for greater than 1 ohm between the keypad supply voltage terminal 12 and ground.
| ⇒ | If less than specified value, repair short to ground or replace the VCIM. |
- Ignition ON, test for 9.8-10.2 volts between keypad supply voltage terminal 12 and ground.
| ⇒ | If less than the specified range, repair open circuit or replace the VCIM. |
| ⇒ | If greater than the specified range, repair short to voltage or replace the VCIM. |
- If all circuit test normal, replace the inside rearview mirror.
Repair Instructions
Perform the
Diagnostic Repair Verification
after completing the diagnostic procedure.
