Diagnostic Instructions

DTC Descriptor

DTC B2455 01:  Cellular Phone Microphone Circuit Short to Battery

DTC B2455 02:  Cellular Phone Microphone Circuit Short to Ground

DTC B2455 04: Cellular Phone Microphone Circuit Open Circuit

Diagnostic Fault Information

Circuit	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performance
Cellular Microphone Signal	B2455 02	B2455 04	B2455 01	-

Circuit/System Description

Without RPO UAV

The vehicle communication interface module (VCIM) uses the cellular phone microphone to allow driver communication with OnStar.

With RPO UAV

The vehicle communication interface module (VCIM) and navigation radio use the cellular phone microphone to allow driver communication with OnStar, as well as to operate the voice recognition/voice guidance feature of the navigation radio.

Conditions for Running the DTC

Conditions for Setting the DTC

B2455 01

A short to battery is detected on the cellular microphone signal circuit

B2455 02

A short to ground is detected on the cellular microphone signal circuit

B2455 04

A open circuit is detected on the cellular microphone signal circuit

Action Taken When the DTC Sets

Conditions for Clearing the DTC

Reference Information

Schematic Reference

OnStar Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

OnStar Description and Operation

Electrical Information Reference

Circuit/System Testing

Without RPO UAV

1. Ignition OFF, disconnect the harness connector at the cellular microphone.
2. Ignition OFF, test for less than 5 ohms between the low reference circuit terminal A and ground.

⇒	If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the VCIM.

3. Ignition ON, test for 9-11 volts between the signal circuit terminal B and ground.

⇒	If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the VCIM.

⇒	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.

4. If all circuits test normal, test or replace the cellular microphone.

With RPO UAV

1. Ignition OFF, disconnect the X4 harness connector at the navigation radio and the harness connector at the cellular microphone.
2. Ignition OFF, test for less than 5 ohms between the low reference circuit terminal A and ground.

⇒	If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the VCIM.

3. Ignition ON, test for 9-11 volts between the signal circuit terminal B and ground.

⇒	If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the VCIM.

⇒	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.

4. If all circuits test normal, test or replace the cellular microphone.
5. Connect the X4 harness connector at the navigation radio. Verify DTC B2455 is not set as current in the navigation radio.

⇒	If DTC B2455 is set as current, replace the navigation radio.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.