GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2007 🢒 STS 🢒 DTC 🢒 DTC B2455

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 provide an overview of each diagnostic category.

DTC Descriptor

DTC B2455 00:  Cellular Phone Microphone Circuit

Circuit/System Description

The vehicle communication interface module (VCIM) detects that the cellular microphone is connected through the cellular microphone signal circuit and the drain wire.

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 in the drain wire circuit or a short to voltage in the cellular microphone signal circuit.
    • The above conditions are present for greater than 10 seconds.

Action Taken When the DTC Sets
    • The VCIM will not receive any signal from the microphone.
    • Calls can be placed but the caller cannot be heard.
    • The OnStar® status LED turns red.

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.
    • The VCIM receives the clear DTC command from the scan tool.

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 Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Circuit/System Testing
  1. Ignition OFF, disconnect the inside rear view mirror harness connector.
  2. Ignition ON, test for less than 9.5 volts at the cellular signal circuit terminal 10.
    3. ⇒If greater than the specified value, repair short to voltage.
  3. Ignition OFF, test for greater than 1 ohm between the cellular signal circuit terminal 10 and ground.
    4. ⇒If less than specified value, repair short to ground.
  4. Disconnect C3 VCIM harness connector.
  5. Test for less than 1 ohm of resistance between the inside rear view mirror harness connector terminal 2 and VCIM harness connector terminal 10.
    6. ⇒If greater than the specified value, repair open/high resistance.
  6. Test for less than 1 ohm of resistance between the inside rear view mirror harness connector terminal 10 and VCIM harness connector terminal 9.
    7. ⇒If greater than the specified value, repair open/high resistance.
  7. If all circuits test normal, test or replace the inside rear view mirror.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Control Module References for VCIM replacement, setup, and programming
    •  Inside Rearview Mirror Replacement