Important: Both the vehicle interface unit (VIU) and the vehicle communication unit (VCU) have a specific set of unique numbers that tie the module to the vehicle where the module resides. These numbers, the 10-digit station identification and the 11-digit electronic serial number, are used by the National Cellular Network and OnStar to identify the specific vehicle. Because these numbers are tied to the vehicle identification number (VIN) of the vehicle, do NOT exchange these parts with those of another vehicle.

1. Remove the rear compartment trim. Refer to Rear Compartment Trim Panel Replacement .
2. Remove the coax cable (1) from the VCU module (3).
3. Disconnect the electrical connectors.
4. Remove the VCU module from the bracket assembly.
5. The old VCU must be returned for core credit.

1. Record the 11-digit ESN number from the label on the new part.



2. Install the VCU module onto the bracket assembly.
3. Connect the coax cable (3) to the VCU (3).

Important: After replacing the VCU, you must reconfigure the OnStar® system. Failure to reconfigure the system will result in an additional customer visit for repair.

4. Reconfigure the OnStar® system. Refer to OnStar Reconfiguration .