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

Removal Procedure

    Object Number: 625727 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. Remove the rear compartment trim. Refer to Rear Compartment Trim Panel Replacement .
  2. Remove the electrical component mounting bracket nuts (2).
  3. Pull the electrical component mounting bracket (1) away from the body and place the electrical component mounting bracket  (1) module side up in the rear compartment.

    4. Object Number: 702924 Size: SH
  4. Remove the VCU/VIU from the electrical component mounting bracket. Release the module retaining tab, and pull the VCU/VIU up and out of the lower section of the electrical component mounting bracket (1).

    5. Object Number: 649484 Size: SH
  5. Remove the VIU/VCU modules (2) from the electrical component mounting bracket (1).
  6. Disconnect the antenna and the electrical connections from the VCU/VIU assembly (2).

    7. Object Number: 649490 Size: SH
  7. Slide the VCU/VIU assembly (2) out of the mounting bracket (1).

    8. Object Number: 649495 Size: SH
  8. Remove the screws retaining the VCU mounting bracket (1) to the VIU (2).
  9. Remove the mounting bracket (1) from the VIU (2).
  10. 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: 649495 Size: SH
  2. Install the VCU mounting bracket (1) to the VIU (2).

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

  3. Install the screws in order to secure the mounting bracket (1) to the VIU (2).

    4. Tighten
    Tighten the screws to 2 N·m (18 lb in)


    Object Number: 649490 Size: SH
  4. Install the VCU (2) to the VIU and bracket assembly (1).

    5. Object Number: 649484 Size: SH

    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.

  5. Connect the electrical connector.

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

  6. Install the VIU/VCU (2) to the electrical component mounting bracket (1).

    7. Object Number: 702924 Size: SH
  7. Push in on the top of the module assembly until an audible click is heard. This click indicates the mounting tab (1) has securely fastened the VIU/VCU to the electrical component mounting bracket.
  8. Install the electrical component mounting bracket (1) to the vehicle body.

    9. Object Number: 625727 Size: SH
  9. Install the electrical component mounting bracket nuts (2).

    10. Tighten
    Tighten the nuts (2) to 9 N·m (80 lb in).

  10. Install the rear compartment trim. Refer to Rear Compartment Trim Panel Replacement .

    11. 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.

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