B2470

DTC B2470

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (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 communication interface module (CIM) with a RG-58 coax cable. The CIM polls the data from the cellular phone antenna once every second.

Conditions for Running the DTC

* Ignition in the RUN or ACC 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 CIM 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(R) Call Center.
* The OnStar(R) status LED turns red.

Conditions for Clearing the DTC

* The CIM detects the presence of a cellular phone antenna.
* A history DTC clears after 50 malfunction-free ignition cycles.

Reference Information
Schematic Reference

OnStar Schematics (OnStar Schematics)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

OnStar Description and Operation (OnStar)
Electrical Information Reference

* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)

Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information

Circuit/System Verification

Verify that the T4F cellular phone antenna and T4F cellular phone antenna coupling assembly are not damaged.

If the antenna assembly is damaged, replace the T4F cellular phone antenna.

Circuit/System Testing

1. Ignition OFF, disconnect the antenna coax from the CIM module and the T4F cellular phone antenna.
2. Ignition ON, test for less than 1 V between the antenna coax center terminal and ground.

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

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

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

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

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

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

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

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

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

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

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

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

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

9. If coax cable tests normal, replace the T4F cellular phone antenna.
10. Clear the DTCs and operate the vehicle within the conditions for running the DTC. Verify DTC B2470 does not set.

• If the DTC sets, replace the CIM.

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Radio Antenna Base Replacement (Radio Antenna Base Replacement)
* Control Module References (Programming and Relearning) for CIM replacement, setup, and programming