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) has the capability of commanding the horn and initiating door lock/unlock. These functions are commanded by the OnStar® Call Center per a customer request.

### Diagnostic Aids

The customer concern may have been due to a lack of cellular service in a given area.

### 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

Important:

• | When contacting the OnStar Call Center, explain to the OnStar advisor that this call is for vehicle diagnostic purposes.

• | It is necessary 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.

1. Verify that the horn, lights, and the doors locks on the vehicle operate properly.

⇒ | If the applicable system does not operate properly, refer to Diagnostic System Check - Vehicle.

2. Contact the OnStar® Call Center by pressing the blue OnStar® button. Verify with the OnStar® advisor that all of the remote functions (door locks and horn)work.

⇒ | If unable to connect with the OnStar® call center, refer to Unable to Contact OnStar Call Center.

⇒ | If the door locks do not operate when requested, refer to Remote Door Locks Malfunction.

3. If the horn does not operate when requested, refer to Remote Horn Malfunction.

### Circuit/System Testing

#### Remote Door Locks Malfunction

1. Ignition OFF, disconnect the harness connector at the OnStar interface module.
2. Ignition ON, test for less than 1 volt between the signal circuit terminal 3 and ground.

⇒ | If greater than the specified range, test the signal circuit for a short to voltage.

3. Test for infinite resistance between the signal circuit terminal 3 and ground.

⇒ | If not the specified value, test the signal circuit for a short to ground.

4. If all circuits test normal, replace the OnStar interface module.

#### Remote Horn Malfunction

1. Ignition OFF, disconnect the harness connector at the OnStar interface module.
2. Ignition ON, test for less than 1 volt between the signal circuit terminal 4 and ground.

⇒ | If greater than the specified range, test the signal circuit for a short to voltage.

3. Test for infinite resistance between the signal circuit terminal 4 and ground.

⇒ | If not the specified value, test the signal circuit for a short to ground.

4. If all circuits test normal, replace the OnStar interface module.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for OnStar integration module replacement, setup, and programming