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HOMESERVICE MANUALSGMC1999FORWARD CONTROL 5.7 R, AUTOMATICREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 743 (SEAT SYSTEM)REPAIR INSTRUCTIONSLUMBAR PUMP 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 2004 Chevrolet Corvette. However, it is still accessible from the selected car via links, so may be relevant.

The lumbar pump and control module are separate units that are attached to each other by a wire harness and a hose. They are supplied and replaced as an assembly. The lumbar pump is contained in a vinyl pouch under the seat and is tie strapped to the seat adjuster torque tube. The attached control module is contained in a vinyl pouch and is secured with J strips to the bottom of the seat support springs. The service part is supplied with connector fittings and the air hoses are labeled #3, #4, and #5 to aid in assembly.

    Fig 1: Seat Electrical Connector
    GM71218Courtesy of GENERAL MOTORS CORP.
  1. Raise the seat to the full up position.
  2. Remove the seat. Refer to Seat Replacement (Power)  or Seat Replacement (Manual) .
  3. Remove the seat cushion cover. Refer to Seat Cushion Trim Cover and Pad Replacement .
    4. Fig 2: Control Module To Seat Cushion Support Wires
    GM339496Courtesy of GENERAL MOTORS CORP.
  4. Remove the tie straps attaching the pump to the torque tube (4) under the seat.
  5. Remove the control module by unhooking the J strips from the seat cushion support wires.
    6. Fig 3: Lumbar Pump & Module To Seat Frame & Seat Back
    GM339492Courtesy of GENERAL MOTORS CORP.
  6. Disconnect the electrical connector.
  7. Reposition the pump and the lumbar control module from under the seat support wires to on top of the seat support wires.
    8. Fig 4: Control Module To Bladder Air Hoses
    GM423945Courtesy of GENERAL MOTORS CORP.
  8. Cut the control module to bladder air hoses (1) 75 mm (3 in) from the control module (5).
  9. Remove the pump (4) and the control module (5) as an assembly.
RENDER: 1.0x

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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.