GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2001 🢒 Eldorado 🢒 Body and Accessories 🢒 Cellular Communication 🢒 OnStar Vehicle Interface Unit Replacement

Removal Procedure

    Object Number: 643043 Size: SH

    Important: The vehicle interface unit (VIU) has a specific set of unique numbers that tie the module to each vehicle. 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 of the vehicle, you must never exchange these parts with those of another vehicle.

  1. Open the rear compartment lid.
  2. Remove the rear seat back trim. Refer to Rear Compartment Front Trim Panel Replacement .
  3. Remove the 4 fasteners (1) securing the tub assembly (2) to the rear seat back panel (3).
  4. Lower the module bracket assembly into the rear compartment.
  5. Disconnect the global position sensor (GPS) antenna coaxial cable from the (VIU).
  6. Disconnect the 2 electrical connectors.
  7. Remove the OnStar® VIU by depressing the retainer tabs.
  8. Remove the VIU.
  9. The old VIU must be returned for core credit.

Installation Procedure
  1. Record the 10-digit STID number from the label on the VIU module.

    2. Object Number: 643043 Size: SH
  2. Install the OnStar® VIU into the module bracket assembly.
  3. Ensure the locking tabs are secure to the VIU.

    4. Notice: In order to avoid damage to the circuit board, do NOT over-tighten the thumb screws. Using your fingers, apply only a light pressure.

  4. Connect the 2 electrical connectors.

    5. Tighten
    Apply 0.2 N·m (2 lb in) of torque or less, to the VIU thumb screw electrical connections.

  5. Connect the GPS antenna coaxial cable to the VIU until fully seated.
  6. Install the module bracket assembly (2) to the seat back panel (3).

    7. Notice: Refer to Fastener Notice in the Preface section.

  7. Install the module bracket fasteners (1).

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

  8. Install the seat back trim. Refer to Rear Compartment Front Trim Panel Replacement .

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

  9. Reconfigure the OnStar® system. Refer to OnStar Reconfiguration .
  10. Return the old VIU for core credit.