Diagnostic Instructions
DTC Descriptor
DTC B2455 00: Cellular Phone Microphone Circuit
Circuit/System Description
The vehicle communication interface module (VCIM) provides the cellular microphone with a supplied voltage on the cellular microphone signal circuit. When the microphone is in use, voice data from the user is sent back to the VCIM on the signal circuit.
The VCIM provides a ground for the microphone via the low reference circuit.
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 10 seconds. |
Conditions for Setting the DTC
| • | The VCIM detects an open, short to ground or short to voltage in the cellular microphone signal circuit for 10 seconds or greater. |
| • | The VCIM detects an open/high resistance in the low reference circuit for 10 seconds or greater. |
Action Taken When the DTC Sets
| • | The OnStar® status LED turns red. |
| • | The VCIM will not receive any signal from the microphone. |
| • | Calls can be placed but the caller cannot be heard. |
Conditions for Clearing the DTC
| • | The VCIM detects the microphone connected for 5 consecutive 100 millisecond cycles. |
| • | 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.
- Ignition ON, test for 9.5-10.5 volts between the signal circuit terminal 10 and ground.
| ⇒ | If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the VCIM. |
| ⇒ | If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the VCIM. |
- Test for test for 9.5-10.5 volts between the signal circuit terminal 10 and the low reference circuit terminal 2.
| ⇒ | If less than the specified range, test the low reference circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the VCIM. |
- If all circuit test normal, replace the cellular microphone.
Repair Instructions
Perform the
Diagnostic Repair Verification after completing the diagnostic procedure.
