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Home >> Cadillac >> 2002 >> Escalade EXT >> Repair and Diagnosis >> External Pages >> Different car >> Section 1144 (Cellular Communication System) >> Repair Instructions >> OnStar Vehicle Communication Unit (VCU) Replacement >> Installation Procedure
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Installation Procedure

WARNING: This page is about a different car, the 2003 Pontiac Grand Prix. However, it is still accessible from the selected car via links, so may be relevant.
  1. Record the 11-Digit ESN number from the label on the new part.
  2. Install the cellular coaxial cable to the VCU pressing into place until fully seated.
    Fig 1: Installing Cellular Coaxial Cable To Vehicle Communication Unit
    G01503462Courtesy of GENERAL MOTORS CORP.
  3. Install the DB-25 connector to the VCU pressing into place until fully seated.
    Fig 2: Installing DB-25 Connector To Vehicle Communication Unit
    G01503463Courtesy of GENERAL MOTORS CORP.
    NOTE: 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. Hand tighten the screws to the DB-25 connector.
    Fig 3: Tightening Screws To DB-25 Connector
    G01503464Courtesy of GENERAL MOTORS CORP.
  5. Position the (VCU) to the top of the vehicle interface unit (VIU).
  6. Install the retainer strap to the VCU pressing into place until fully seated.
    Fig 4: Installing Retainer Strap To Vehicle Communication Unit
    G01503465Courtesy of GENERAL MOTORS CORP.
  7. Install the cover to the VCU bay pressing the cover into place until fully seated.

    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.

  8. Press and hold the white dot button until the OnStar® status LED turns from green to red, and back again to green.
  9. Install a scan tool. Use the ID information menu to access the new ESN.
    Fig 5: Installing Cover To Vehicle Communication Unit
    G01503466Courtesy of GENERAL MOTORS CORP.
  10. Move the vehicle to an open area that is away from tall buildings and with a clear view of unobstructed sky. Allow the vehicle to run for 10 minutes.
  11. Press the blue OnStar® button to connect to the OnStar® call center
    1. 11.1. Tell the advisor that this vehicle has received a new VCU.
    2. 11.2. Ask the advisor to add the new ESN to update the customer's account.
    3. 11.3. Follow any additional instructions from the OnStar® advisor.
    4. 11.4. Ask the advisor to activate the OnStar® personal calling feature, if available.
  12. Close the rear compartment.
  13. Return the old VCU for core credit.
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