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.

### Circuit/System Description

The vehicle communication interface module (VCIM) is a 3-watt cellular device that allows the user to communicate data and voice signals over the national cellular network. When an OnStar keypress is made, the VCIM activates and connects the system to the cellular carriers communication system by interacting with the national cellular infrastructure. The VCIM sends and receives all cellular communications over the cellular antenna and cellular antenna coax.

### Diagnostic Aids

• | The customer concern may have been due to a lack of cellular service in a given area. A failure in the national cellular network infrastructure at the time of the customers failed connection that has since been repaired may also have been the cause.

• | If the prompt "OnStar® request ended" is heard, without pressing the white dot button at the end of the OnStar® keypress, the OnStar® system at one time has made a successful cellular connection, but was unable to complete the call. If repeated calls are placed with this result, contact General Motors Technical Assistance Center.

• | It is important to have the vehicle in an open outside area where a cellular call can be successfully placed and GPS data can be received from satellites.

### 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

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

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

2. Ignition ON, press the OnStar® Call Center button. Verify the system activates and the message Connecting to OnStar® is heard.

⇒ | If the system does not activate and the message is not heard, refer to OnStar One or More Buttons Inoperative .

### Circuit/System Testing

1. Disconnect the harness connector at the radio antenna.
2. Ignition OFF, test for less than 10 ohms between the terminal 3 outer shield and ground.

⇒ | If greater than the specified range, test the antenna coax shield for an open/high resistance. If the coax tests normal, replace the VCIM.

3. Ignition ON, test the terminal 3 center terminal for 0.5-1.0 volts.

⇒ | If greater than the specified range, test the antenna coax center terminal for a short to voltage. If the coax tests normal, replace the VCIM.

⇒ | If less than the specified range, test the antenna coax center terminal for a short to ground or an open/high resistance. If the coax tests normal, replace the VCIM.

4. If all circuits test normal, replace the antenna.
5. Ignition ON, press the OnStar® Call Center button. Verify the Connecting to OnStar® is heard and a successful connection is made to OnStar®.

⇒ | If a connection is not established, replace the VCIM.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Radio Antenna Replacement

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