Important: Never swap OnStar® vehicle integration units (VIU), or the vehicle communication units (VCU) from other vehicles. Transfer of OnStar® components from other vehicles should NOT be done. Each OnStar® component has a unique identification number. The VIU has a 10-digit specific station identification (STID) and the VCU has a 11-digit specific electronic serial number (ESN). These identification numbers are used by the National Cellular Telephone Network and OnStar® systems, and are stored in the General Motors vehicle history files by VIN.

1. Open the rear compartment lid.
2. Remove the seat back trim panel. Refer to Rear Compartment Front Trim Panel Replacement in Body Rear End.
3. Remove the 4 nuts (1) securing the module bracket assembly (2) to the rear seat back panel (3).
4. Lower the module bracket assembly into the rear compartment.
5. Disconnect the cellular coaxial cable from the VCU by pulling upward on the spring loaded snap connector.
6. Disconnect the electrical connector.
7. Remove the OnStar® VCU by lifting the retainer tab.
8. Remove the VCU.
9. The old VCU must be returned for core credit.

1. Record the 11-digit ESN from the label on the new VCU module.



2. Install the OnStar® VCU to the module bracket assembly.
3. Ensure the locking tab is secure to the VCU.
4. Connect the electrical connector.
5. Connect the cellular coaxial cable to the VCU until fully seated.
6. Install the module bracket assembly (2) to the seat back panel (3).

Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.

7. Install the nuts (1).

Tighten
Tighten the nuts to 9 N·m (80 lb in).

8. Install the seat back trim. Refer to Rear Compartment Front Trim Panel Replacement in Body Rear End.
9. Close the rear compartment lid.
10. Press and hold the "end call" button, which is a black button with a white dot.

The OnStar® status light will change from green to red to green.

11. Contact the OnStar® Dealer support line by pressing the blue OnStar® button twice.

The 11-digit ESN number will be needed by the OnStar® advisor.