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HOMESERVICE MANUALSGMC1999FORWARD CONTROL 5.7 R, AUTOMATICREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 693 (CELLULAR COMMUNICATION SYSTEM)REPAIR INSTRUCTIONSONSTAR VEHICLE COMMUNICATION UNIT (VCU) REPLACEMENTREMOVAL PROCEDURE
1999 GMC Forward Control 5.7 R, Automatic

Removal Procedure

1999 GMC Forward Control 5.7 R, AutomaticSECTION Removal 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.

Important:  The vehicle communication unit (VCU) 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.
  2. Remove the cover from the OnStar® vehicle communication unit (VCU) by depressing the retainer tabs.
    Fig 1: Removing Cover From OnStar® Vehicle Communication Unit
    G01503457Courtesy of GENERAL MOTORS CORP.
  3. Remove the cellular coaxial cable from the VCU by pulling off.
    Fig 2: Removing Cellular Coaxial Cable From Vehicle Communication Unit
    G01503458Courtesy of GENERAL MOTORS CORP.
  4. Remove the screws from the DB-25 connector.
    Fig 3: Removing Screws From DB-25 Connector
    G01503459Courtesy of GENERAL MOTORS CORP.
  5. Remove the DB-25 connector from the VCU.
    Fig 4: Removing DB-25 Connector From Vehicle Communication Unit
    G01503460Courtesy of GENERAL MOTORS CORP.
  6. Release the retainer strap from the VCU using a small flat-bladed tool.
  7. Remove the VCU from the rear compartment.
    Fig 5: Releasing Retainer Strap From Vehicle Communication Unit
    G01503461Courtesy of GENERAL MOTORS CORP.
RENDER: 1.0x

NO RELATED

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.