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 provides an overview of each diagnostic category.

DTC Descriptor

DTC B2470 04

Cellular Phone Antenna Circuit Open Circuit

Circuit/System Description

The cellular phone antenna is connected to the telematics communication interface control module with a RG-58 coax cable. The telematics communication interface control module polls the data from the cellular phone antenna once every second.

Conditions for Running the DTC

•	The ignition is in the RUN or ACCESSORY position.

•	System voltage is between 9.5 V and 15.5 V.

•	The above conditions are present for greater than 1 second.

Conditions for Setting the DTC

The telematics communication interface control module does not detect the presence of a cellular phone antenna.

Action Taken When the DTC Sets

•	The vehicle is unable to connect to the OnStar® Call Center.

•	The OnStar® status LED turns red.

Conditions for Clearing the DTC

•	The telematics communication interface control module detects the presence of a cellular phone antenna.

•	A history DTC clears after 50 malfunction-free ignition cycles.

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 Testing

•	Connector Repairs

•	Testing for Intermittent Conditions and Poor Connections

•	Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Special Tools

EL-49903 GM OnStar Antenna Diagnostic Tool Kit

Circuit/System Verification

Verify that the T4G cellular phone antenna and T4G cellular phone antenna coupling assembly are not damaged.

Circuit/System Testing

1.	Ignition OFF, disconnect both the GPS and cell coax cable connectors at the K73 telematics communication interface control module.

2.	Connect the EL-49903 to the K73 telematics communication interface control module.

3.	Erase the diagnostic trouble codes and run the car under the same conditions as during the diagnostic trouble code. Check that diagnostic trouble code B2470 is not set.

4.	If the DTC sets, replace the K73 telematics communication interface control module.

5.	Ignition OFF, disconnect the EL-49903 from the K73 telematics communication interface control module, and the antenna coax from the T4G cellular phone antenna.

6.	Ignition ON, test for less than 1 V between the antenna coax center terminal and ground.

7.	If greater than the specified range, replace the antenna coax.

8.	Ignition ON, test for less than 1 V between the antenna coax outer shield and ground.

9.	If greater than the specified range, replace the antenna coax.

10.	Test for infinite resistance between the antenna coax center terminal and ground.

11.	If less than the specified value, replace the antenna coax.

12.	Test for infinite resistance between the antenna coax outer shield and ground.

13.	If less than the specified value, replace the antenna coax.

14.	Test for less than 5 Ω at the cellular antenna coax center terminal from end to end.

15.	If greater than specified value, replace the antenna coax.

16.	Test for less than 5 Ω at the cellular antenna coax outer shield from end to end.

17.	If greater than specified value, replace the antenna coax.

18.	Test for infinite resistance between the antenna coax center terminal and the outer shield.

19.	If less than specified value, replace the antenna coax.

20.	If coax cable tests normal, replace the T4G cellular phone antenna.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

•	Radio Antenna Base Replacement

•	Control Module References for telematics communication interface control module replacement, setup, and programming