For 1990-2009 cars

### 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 Malfunction Open Circuit

### Circuit/System Description

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

### Conditions for Running the DTC

• | Ignition in the RUN or ACC position.

• | System voltage is between 9.5 volts and 15.5 volts.

• | 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 antenna.

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

### 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 CIM detects the presence of a cellular 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

### Circuit/System Verification

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

⇒ | If the antenna assembly is damaged, replace the cellular antenna.

### Circuit/System Testing

1. Ignition OFF, disconnect the cellular antenna coax from the CIM module and the cellular antenna.
2. Ignition ON, test for less than 1 volt 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 volt 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 cellular antenna coax cable.

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 cellular antenna coax cable.

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

⇒ | If less than specified value, replace the cellular antenna coax cable.

9. If coax cable tests normal, replace the cellular 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 after completing the diagnostic procedure.

• | Antenna Cable Replacement

• | Radio Antenna Base Replacement

• | Control Module References for CIM replacement, setup, and programming