GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2001 🢒 Sonoma Pickup - 2WD 🢒 Body and Accessories 🢒 Body Control System 🢒 OnStar Vehicle Interface Unit Replacement

Removal Procedure

    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 top cover of the body side trim panel on the right side of the vehicle to expose the VCU/VIU assembly.

    2. Object Number: 655277 Size: SH
  2. Remove the 2 nuts (1) and lift the VCU/VIU assembly up and out of the vehicle.

    3. Object Number: 655250 Size: SH
  3. Disconnect the cellular antenna coaxial cable (2) and electrical connector (6) from the VCU (7).
  4. Disconnect the global position sensor (GPS) cable connector (4) and electrical connector (3) from the VCU/VIU assembly
  5. Remove the 4 screws that attach the VIU to the assembly bracket.
  6. Remove the VIU (1) from the vehicle.
  7. 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. Install the VIU (4) to the VCU/VIU assembly mounting bracket.

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

  3. Install the 4 screws that attach the VIU to the assembly bracket.

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


    Object Number: 655250 Size: SH
  4. Reconnect the cellular antenna coaxial cable (2) and electrical connector (6) to the VCU.
  5. Reconnect the GPS cable connector (4) and the electrical connector (3) to the VCU/VIU assembly.

    6. Object Number: 655277 Size: SH
  6. Install the VCU/VIU assembly to the vehicle. Ensure that the lower arm (3) of the mounting bracket is inserted into the slot (2) provided in the body sheet metal.
  7. Install the VCU/VIU assembly to the vehicle using the 2 nuts (1).

    8. Tighten
    Tighten the nuts to 10 N·m (89 lb in).

  8. Install the top cover of the body side trim panel to cover the VCU/VIU assembly.

    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 .